Use of Antimicrobials and Carriage of Penicillin-Resistant Pneumococci in Children

Repeated cross-sectional studies covering 10 years

Vilhjalmur Ari Arason

PhD Thesis University of Iceland, Faculty of Medicine, Department of Family Medicine October 2006 From Department of Family Medicine, University of Iceland, Primary Healthcare Centre of Solvangur and Healthcare Centre Fjördur, IS-220 Hafnarfjördur, Iceland

Use of Antimicrobials and Carriage of Penicillin-Resistant Pneumococci in Children Repeated cross-sectional studies covering 10 years

Vilhjalmur Ari Arason

Supervisor Johann A. Sigurdsson Co-supervisor Karl G. Kristinsson

PhD committee: Thorolfur Gudnason (chair), Directorate of Health, Iceland Johann A. Sigurdsson, University of Iceland Vilhjalmur Rafnsson, University of Iceland Magnus Johannsson, University of Iceland Haraldur Briem, Directorate of Health, Iceland

Reykjavík 2006 Vilhjálmur Ari Arason:

Use of Antimicrobials and Carriage of Penicillin-resistant Pneumococci in Children. Repeated cross-sectional studies covering 10 years

The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the author.

Háskólaútgáfan Reykjavík 2006 ©Vilhjálmur Ari Arason e-mail: [email protected] Umbrot: Þröstur Haraldsson Prentun og bókband: Leturprent ISBN 9979-70-157-9 ISBN 978-9979-70-157-6 ÁGRIP

Notkun sýklalyfja og beratíðni penicillín ónæmra pneumókokka hjá börnum – Endurteknar þversniðsrannsóknir á 10 ára tímabili

Vilhjálmur Ari Arason Heimilislæknisfræði, Háskóla Íslands, Heilsugæsla höfuðborgar svæðisins, Sólvangur og Fjörður, Hafnarfirði, Íslandi.

Tilgangur: Að athuga notkun sýklalyfja meðal forskólabarna á Ís landi og meta hugsanlegt samband slíkrar notkunar við beratíðni penicillín ónæmra pneumókokka í nefkoki þeirra. Efniviður og aðferðir: Upplýsingar voru fengnar hjá foreldrum og úr sjúkraskrám heilsugæslustöðva um sýklalyfjaávísanir 2.612 barna á aldrinum 1-6 ára sem bjuggu á mismunandi stöðum á landinu. Úr þessum hóp voru teknar nefkoksræktanir frá 2.486 börnum. Gerðar voru þrjár þversniðsrannsóknir á sömu svæðum á 10 ára tímabili (I. hluti 1993, II. hluti 1998 og III. hluti 2003). Þátttökuhlutfall var frá 75 til 88%. Einnig var unnið úr upplýsingum apóteka sömu svæða varðandi 22.132 ávísanir á sýklalyf til inntöku (utan spítala) fyrir alla aldurshópa árið 1993 og 15.153 ávísanir árið 1998. Aðal mælibreytur: Tíðni penicillín ónæmra pnemókokka í nefkoki og áhættuþættir berasmits, heildarnotkun sýklalyfja, notkun þeirra vegna bráðrar miðeyrnabólgu (acute otitis media), væntingar foreldra og notkun hljóðhimnuröra. Niðurstöður: • Sýklalyfjaávísunum heimilislækna til barna fækkaði um 1/3 á rannsóknartímabilinu. Munur var á ávísanavenjum lækna milli svæða, sérstaklega varðandi meðferð við bráðri miðeyrna bólgu. • Fylgni var á milli væntinga foreldra til sýklalyfjanotkunar og ávísana lækna á sýklalyf til barna eftir búsetu. • Yfir 30% barna á Íslandi fá hljóðhimnurör á fyrstu 6 aldursár unum. Á svæðum þar sem sýklalyfjanotkunin var mikil var meiri notkun á breiðvirkum sýklalyfjum borið saman við hin

iii svæðin og notkun röra í hljóðhimnur fór vaxandi (upp í 44% allra barna). Á öðrum stöðum, þar sem sýklalyfjanotkunin hafði minnkað, var röranotkunin komin mest niður í 17%. • Sterkt samband var á milli sýklalyfjanokunar einstaklinga og tíðni penicillín ónæmra pneumókokka í nefkoki þeirra. • Fjölónæmir (ónæmir fyrir mörgum tegundum sýklalyfja) og jafnframt penicillín ónæmir pneumókokkar af sermisgerð 6B (með sömu svipgerð og Spain6B-2 stofninn) fundust á svæðun um. Tíðni þeirra náði vissu hámarki en minnkaði síðan aftur eða að þeir hurfu með öllu á þessu 10 ára tímabili, bæði á svæðum þar sem sýklalyfjanotkunin var mikil og eins þar sem hún var lítil. Ályktanir: Sterkt samband ríkir á milli sýklalyfjanotkunar og tíðni penicillín ónæmra pneumókokka í nefkoki barna. Eftir sýkla lyfjanotkun er barnið næmara fyrir utanaðkomandi smiti svo sem í leikskólum. Líklegt er að faraldsfræðileg dreifing nýrra ónæmra pneumókokkastofna skýri megin sveiflur í beratíðninni. Hugsanlega er samband á milli (of)notkunar sýklalyfja við bráðri miðeyrnabólgu og endurtekinna eyrnabólgusýkinga síðar meir og ísetningu hljóð himnuröra.

Lykilorð: Sýklalyfjanotkun, lyfjaávísanir, bráð miðeyrnabólga, börn, sýklalyfjaónæmi, penicillín ónæmir pneumókokkar, sermisgerð 6B, útbreiðsla bakteríustofna, Spain6B-2, hjarðarónæmi, hljóðhimnurör, heilsugæsla, heimilislækningar.

iv ABSTRACT

Use of antimicrobials and carriage of penicillin-resistant pneumococci in children – Repeated cross-sectional studies covering 10 years

Vilhjalmur Ari Arason Department of Family Medicine, University of Iceland, Primary Healthcare Centre of Solvangur and Fjordur, IS-220 Hafnarfjordur, Iceland.

Objectives: The overall aim of this thesis was to analyse the use of antimicrobials in pre-school children in Iceland and the connection between such use and the carriage of penicillin-nonsusceptible pneumococci (PNSP). Study populations and methods: Prescription data and medical histories from 2,612 children, aged 1 to 6 years, living in different geographically well-defined study areas in Iceland, and nasopharyngeal specimens from 2,486 children were analysed in three cross- sectional studies covering 10 years (Phase I 1993, II 1998, and III 2003). Participation varied from 75% to 88%. Annual analysis of oral antimicrobial sales/prescriptions for whole communities (hospital use excluded) were based on 22,132 prescriptions in 1993, and 15,153 in 1998. Main outcome measures: The prevalence and risk factors for nasopharyngeal carriage of PNSP, total antimicrobial use, antimicrobial use for acute otitis media (AOM), parental expectations and tympanostomy tube placements. Results: • Antimicrobial prescription rates among GPs diminished by about 1/3 over the study period. Prescription habits varied greatly between communites especially because of AOM. • Parents’ expectations of antimicrobial prescriptions were associated with the antimicrobial prescription rate in each area. • The cumulative prevalence of tympanostomy tube placement among pre-school children is high in Iceland (over 30%). In

areas where the prescription rate was high, broad-spectrum antimicrobials were prescribed relatively more often than in other areas, and the tympanostomy tube placement rate was increasing (up to 44% of all children). In other areas, tympanostomy tube rate among children deceased (down to 17%) at the same time as antimicrobial use for AOM diminished. • There was a strong association between antimicrobial use on the individual level and the nasopharyngeal carriage of PNSP. • PNSP, multiresistant, serotype 6B (phenotypically identical to the Spain6B-2 clone) appeared and disappeared over a 10-year period, in communities with both high and low antimicrobial use. Conclusions: There is a strong association between antimicrobial use for individual children and the nasopharyngeal carriage of PNSP. Pneumococcus is acquired from other children, usually in day-care settings and PNSP selectively colonised when receiving antimicrobials. Spread of novel resistant clones appears to be the main reason for marked changes in pneumococcal resistance rates in individual communities over time. Antimicrobial drug (over)use for AOM my be associated with future episodes of AOM and tympanostomy tube placements.

Key words: antimicrobial use, drug prescription, acute otitis media, children, antimicrobial resistance, penicillin-nonsusceptible pneumococci, clonal spread, Spain6B-2, herd immunity, tympanostomy tube placement, primary healthcare, general practice.

vi ACKNOWLEDGEMENTS

I wish to express my sincere gratitude to all those who have made this thesis possible. I especially want to thank: My supervisor Professor Jóhann Ágúst Sigurðsson, head of De- partment of Family Medicine, University of Iceland. Without his experience, enthusiasm, positive and encouraging attitude and patience, this thesis may never have come true. Our long co-operation has developed into a good friendship. My other co-authors, Professor Karl G. Kristinsson, Dr. Sigurður Guðmundsson, Helga Erlendsdóttir, Guðrún Stefánsdóttir, Aðal steinn Gunnlaugsson, Dr. Linn Getz and Professor Sigvard Mölstad for valuable expertise and co-operation in the research. Professor emeritus Calle Bengtsson former head of the Depart- ment of Primary Healthcare, Gothenburg for his generous support and enthusiasm in beginning writing the thesis. My colleagues and others at the Fjordur Healthcentre and Solvang ur Healthcentre Hafnarfjordur for encouragement and help with my patients. Special thanks to all the children who participated in the study, their parents, the general practitioners who assisted in the study areas and to the staff of the Department of Clinical Microbiology, Landspitali University Hospital. Last but not least, my wife Ingibjörg Ásgeirsdóttir for supporting me so unselfishly and tolerating me all the time I have spent working in this research last 15 years. Also my children, Ásgeir Snær and his wife Eyrún, Jóhanna and her boyfriend Hördur, Ásta and my grand- children Steinn Andri, Hjördís María, Ingibjörg Svana and Emilía for their patience and encouragement. This study was mainly supported by the Icelandic College of Family Physicians. It was also granted by The Research Fund of the University of Iceland, and the Research Fund of the Landspitali University Hospi- tal, Reykjavik.

vii CONTENTS

ÁGRIP...... iii ABSTRACT...... v ACKNOWLEDGEMENTS...... vii CONTENTS...... viii LIST OF FIGURES AND TABLES ...... xi LIST OF PAPERS...... xvi CONTRIBUTORS...... xvii ABBREVIATIONS AND DEFINITIONS...... xviii INTRODUCTION...... 1 Bacterial resistance to antimicrobials ...... 2 Biochemical processes behind bacterial resistance...... 3 Streptococcus pneumoniae...... 4 Pneumocaccae vaccination...... 5 Penicillin resistance among pneumococci...... 6 Otitis media...... 6 Acute otitis media and antimicrobial use ...... 9 Tympanostomy tube placements...... 10 Background for a study of antimicrobial use in relation to resistant bacteria in Iceland...... 11 Sales statistics of antimicrobials...... 11 Penicillin-resistant pneumococci in Iceland...... 12 RESEARCH QUETION AND AIM OF THE STUDY...... 14 Main research question...... 14 Aim of the study...... 14 STUDY POPULATION...... 16 Demography of Iceland...... 16 Characteristics of the study areas...... 16 Choice of study areas...... 18 Organisational structure of the healthcare service...... 19 Details on data collection from the different areas...... 19 Selection criteria for the study groups...... 20 Overview of the data presented in the thesis...... 22 METHODS...... 23 Antimicrobial sales statistics ...... 23

viii Microbiology and nasopharyngeal sampling for pneumococci ...... 23 Information about infection disease history and socio-demographic factors...... 24 Statistical methods...... 24 Ethical considerations...... 25 RESULTS...... 26 Sales statistics of antimicrobial use in communities (I, II).... 26 Antimicrobial sales according to age, gender and time of year (1997-1998) ...... 26 Type of antimicrobial drugs sales (1997-1998)...... 28 Changes in antimicrobial sales for children between 1993 and 1998...... 28 Antimicrobial use among pre-school children in the sampled groups (I, III, IV) ...... 29 Main diagnoses when prescribing antimicrobials for children...... 31 Antimicrobial use for acute otitis media...... 31 Predictors for antimicrobial prescribing for acute otitis media...... 34 Association between parental expectation and doctors’ prescription habits for management of upper respiratory tract infections in children...... 35 Tympanostomy tube placements (III, IV)...... 36 Association between tympanostomy placements and antimicrobial use...... 38 Effects of tympanostomy tubes on recent antimicrobial drug consumption...... 38 Antimicrobial resistance in pneumococci (I, II, V)...... 38 Carriage of penicillin-nonsusceptible pneumococci (PNSP)...... 38 Carriage of erythromycin-resistant pneumococci...... 40 Penicillin-resistance among pneumococci and antimicrobial use...... 41 Associations with PNSP-carrying in children carrying pneumococci...... 43 Risk of PNSP carriage after receiving antimicrobials for all children (i.e., not only those carrying pneumococci)... 45

ix Factors associated with carriage of erythromycin- resistant pneumococci...... 48 Spread of resistant strains...... 48 Clonal spread of PNSP of multiresistant 6B strain (Spain6B-2) in different communities...... 49 DISCUSSION...... 51 Starting points when planning the studies...... 51 Performance of the studies...... 52 Antimicrobial use...... 53 Tympanostomy tube placements...... 58 Antimicrobial use and carriage of antimicrobial-resistant pneumococcus...... 59 Amount and type of antimicrobials associated with resistance in the community...... 62 Clonal spread in the community...... 64 Associations between acute otitis media, antimicrobial use and tympanostomy tube placements...... 67 Acute otitis media in relation to antimicrobial-resistant bacteria ...... 69 Tympanostomy tubes and bacterial antimicrobial resistance 70 Limitations in the study design...... 70 Summary of association studied...... 71 SUMMARY OF AIMS, MAIN RESULTS AND CONCLUSIONS...... 74 CLINICAL IMPLICATIONS...... 77 REFERENCES ...... 79 PAPERS I-V...... 92 APPENDIX...... 137

LIST OF FIGURES AND TABLES

Figures Figure 1. Antimicrobial consumption in the Nordic countries based on total sales statistics from the Ministry of Health and Social Security, Iceland, and The Nordic Council on Medicine...... 11

Figure 2. Total sales of antimicrobial mixtures in Iceland 1989-1997 based on sales statistics from the Ministry of Health and Social Security...... 12

Figure 3. Main research question of the thesis...... 14

Figure 4. Hypothesised associations between the main factors studied in this thesis...... 15

Figure 5. The North-Atlantic countries...... 16

Figure 6. Study areas in Iceland ...... 17

Figure 7. Incidence of antimicrobial prescriptions (information from annual drug-store sales statistics) by age and gender in the 1998 study...... 27

Figure 8. Antimicrobial use as number of defined antimicrobial doses (DDD) per 1000 inhabitants per day by gender and month in the 1998 study (information from annual drug-store sales statistics)...... 27

Figure 9. Antimicrobial use according to age groups in the study areas 1997-1998 (information from annual drug-store sales statistics)...... 28

Figure 10. Yearly incidence of antimicrobial treatments per child in relation to age in 1993, 1998 and 2003... 29

xi Figure 11. Yearly incidence of antimicrobials among children 1-6 years of age in different study areas in the 1993, 1998 and 2003 studies...... 30

Figure 12. Choice of last antimicrobial group prescribed before study entry among 1-6 year old children in the 1993, 1998 and 2003 studies...... 31

Figure 13. Main last diagnosis when prescribing antimicrobials for children, aged 1-6, in the 1993, 1998 and 2003 studies...... 32

Figure 14. Yearly prevalence as the percentage of children receiving antimicrobial treatment for acute otitis media by age and study year...... 32

Figure 15. Yearly incidence of antimicrobial treatment for acute otitis media per child in relation to age and study year...... 33

Figure 16. Yearly incidence of antimicrobial treatments for acute otitis media per child in different areas studied in 1993, 1998 and 2003...... 34

Figure 17. Cumulative prevalence as a percentage of use of tympanostomy tubes among 1-6 years old children 1998 and 2003...... 36

Figure 18. Differences in the use of tympanostomy tubes (cumulative prevalence) in relation to change (%) in the use of antimicrobials (yearly incidence) for acute otitis media between 1998 and 2003 for the different studies areas...... 39

Figure 19. Changes in antimicrobial use among 1-6 year old children in the four study areas and the carriage rate of penicillin-nonsusceptible pneumo-

xii cocci (PNSP) 1993, 1998 and 2003. Data from antimicrobial sales statistics in study areas for children < 7 years old, 1992-1993 and 1997- 1998, are also shown for comparison...... 41

Figure 20. Carriage rate of penicillin-nonsusceptible pneumococci (PNSP) of all children carrying pneumococci, 1-6 years of age, related to time from last antimicrobial treatment (2-7 weeks or 8-52 weeks) or no treatment in the studies in 1993, 1998, and 2003...... 45

Figure 21. Adjusted odds ratio for carrying penicillin-nonsusceptible pneumococci (PNSP) or not according to multivariate logistic regression analysis in studies in 1993, 1998 and 2003...... 46

Figure 22. Carriage rate of penicillin-susceptible (PSP) and penicillin-nonsusceptible pneumococci (PNSP) by all children receiving antimicrobials during the 12 months prior to study entry for the 1993, 1998 and 2003 studies, by the number of weeks from the last antimicrobial treatment...... 47

Figure 23. Spread of different serotypes of penicillin-nonsusceptible pneumococcus (PNSP) as carrying ratio (%) of all pneumococci observed in the studies in 1993, 1998 and 2003...... 48

Figure 24. The prevalence of penicillin-nonsusceptible pneumococci (PNSP) of multiresistant serotype 6B (the Spain6B-2 clone) as a carriage rate of all pneumococci and use of antimicrobials in the sample groups, as observed in the study areas in the 1993, 1998 and 2003 studies. Data from antimicrobial sales statistics in the study areas

xiii for children < 7 years old, 1993 and 1998 are also shown for comparison...... 49

Figure 25. a) Prevalence of penicillin-nonsusceptible pneumococci (PNSP) of multiresistant serotype 6B (recognised as the Spanish-Icelandic clone, Spain6B-2), as a percentage of all children carrying pneumococci, observed in areas H, V, E and B in the studies in 1993, 1998 and 2003. b) A theoretical model (epidemiological curves) for the spread and disappearance of Spain6B-2 clone in four communities in Iceland 1993-2003...... 66

Figure 26. Conclusions concerning potential associations and their directions...... 72

Tables Table 1. Temperature, humidity and wind speed during the years 1993, 1998 and 2003 in four research areas in Iceland; Hafnarfjordur (H), Vestman- naeyjar (V), Egilsstadir (E) and Bolungarvik (B) 18

Table 2. Study population from phases II (1998) and III (2003) and, for comparison, from phase I (1993), where children from area HH and children <1 year of age were excluded from the results presented in Paper I...... 21

Table 3. Details on data collection from the different areas...... 22

Table 4. Antimicrobial use 1993 and 1998 according to sales statistics, measured as the number of defined daily doses (DDD) per 1000 inhabitants per day in the study areas ...... 26

xiv Table 5. Parents’ views on appropriate antimicrobial treatment as reported in questionnaires from the 1998 and 2003 studies...... 35

Table 6. Odds ratio by multivariate analysis, adjusted for age, for children 1-6 years old having tympanostomy tube(s) at present as opposed to not having tube(s) in the 2003 study...... 37

Table 7. Prevalence of penicillin-nonsusceptible pneumococci as observed in the studies in 1993, 1998 and 2003...... 40

Table 8. Penicillin-resistant pattern for pneumococci in children in the 1993 study by age groups...... 40

Table 9. Number (No) of penicillin-susceptible (PSP) and nonsusceptible pneumococci (PNSP), which are nonsusceptible (intermediate or resistant) to erythromycin (ERY), tetracycline (TET) chloramphenicol (CHL) and trimethoprim-sulfamethoxazole (SXT) according to disc diffusion tests, in 1993, 1998 and 2003, in respective study areas...... 42

Table 10. Odds ratio (OR) of carrying penicillin-nonsusceptible pneumococci (PNSP) as opposed to penicillin-susceptible pneumococci by backward, stepwise, logistic regression method in the studies in 1993, 1998 and 2003...... 44

xv xv LIST OF PAPERS

This thesis is based on the following original Papers, which will be referred to by the Roman numerals.

I. Arason VA, Kristinsson KG, Sigurdsson JA, Stefansdottir G, Mölstad S, Gudmundsson S (1996). Do antimicrobials increase the carriage rate of penicillin resistant pneumococci in children? Cross sectional prevalence study. BMJ; 313: 387-91.

II. Arason VA, Gunnlaugsson A, Sigurdsson JA, Erlendsdottir H, Gudmundsson S, Kristinsson KG (2002). Clonal spread of resistant pneumococci despite diminished antimicrobial use. Microb Drug Resist; 8: 187-93.

III. Arason VA, Sigurdsson JA, Kristinsson KG, Gudmundsson S (2002). Tympanostomy tube placements, influence of sociodemographic factors and parental expectations for management of acute otitis media in Iceland. Ped Inf Dis J; 21: 1110-5.

IV. Arason VA, Sigurdsson JA, Kristinsson KG, Getz L, Gudmunds son S (2005). Otitis media, tympanostomy tube placement, and use of antimicrobials. Cross sectional community study repeated after five years. Scand J Prim Healthcare; 23: 184- 91.

V. Arason VA, Sigurdsson JA, Erlendsdottir H, Gudmundsson S, Kristinsson KG (2006). The role of antimicrobial use in the epidemiology of resistant pneumococci: a 10-year follow up. Microb Drug Resist; 12: 169-76.

xvi Contributors

Paper I Vilhjalmur Ari Arason (VAA), Johann A Sigurdsson (JAS), Sigvard Mölstad and Sigurdur Gudmundsson (SG) were responsible for the design of the study. VAA and JAS were responsible for recruitment and sampling. Gudrun Stefansdottir, Karl G. Kristinsson (KGK) and SG were responsible for the bacteriological studies. VAA and other authors were responsible for analysing the data. VAA wrote the first draft of the paper and together with KGK, JAS and SG was responsible for writing the paper. All authors were responsible for editing the paper and were involved in final approval of the paper. VAA and JAS are guarantors.

Paper II VAA, JAS, KGK and SG were responsible for the design of the study. VAA, Adal- steinn Gunnlaugsson (AG) and JAS were responsible for recruitment and sampling. Helga Erlendsdottir (HE), AG and KGK were responsible for the bacteriological studies. VAA and other authors were responsible for analysis of the results. VAA wrote the first draft and then VAA and KGK were responsible for writing the paper. All were responsible for editing the paper and all were involved in final approval of the paper. KGK and VAA are guarantors.

Paper III VAA and the other authors were responsible for the design of the study. VAA and JAS were responsible for recruitment and sampling. VAA and other authors were responsible for analysing the results. VAA wrote the first draft and VAA, JAS and SG were responsible for writing the paper. All authors were responsible for editing the paper and were involved in final approval of the paper. VAA and JAS are guarantors.

Paper IV VAA and the other authors were responsible for the design of the study. VAA and JAS were responsible for recruitment and sampling. VAA and the other authors were responsible for analysing the results. VAA wrote the first draft and then VAA, JAS and Linn Getz were responsible for writing the paper. All authors were responsible for editing the paper and were involved in final approval of the paper. VAA and JAS are guarantors.

Paper V VAA and the other authors were responsible for the design of the study. VAA and JAS were responsible for recruitment and sampling. HE and KGK were responsible for the bacteriological studies. VAA and the other authors were responsible for analysing the data. VAA wrote the first draft and then VAA and KGK were responsible for writing the paper. All authors were responsible for editing the paper and were involved in final approval of the paper. KGK and VAA are guarantors.

xviixvii ABBREVIATIONS AND DEFINITIONS

Abbreviations AOM Acute otitis media B Bolungarvik CI Confidence interval DDD Defined daily dose E Egilsstadir G Gardabaer GP General practitioner H Hafnarfjordur HG Hafnarfjordur and Gardabaer HH Hella and Hvolsvöllur MIC Minimal inhibitory concentration NS Not significant OR Odds ratio PNSP Penicillin-nonsusceptible pneumococci PSP Penicillin-susceptible pneumococci SD Standard deviation V Vestmannaeyjar

Definitions Antimicrobials = antibiotics Strain = serotype Clone = subtype (serotype) of a bacteria with the same DNA origin (fingerprint) DDD/1000/day = defined daily dose per 1000 individuals daily Herd immunity = immunity status in the population against specific organisms Intermediate-resistant pneumococci = penicillin MIC ≥ 0.1-1.0 mg/l Multiresistant (multidrug-resistant) = resistant to three or more different antimicrobial groups Penicillin-nonsusceptible pneumococci (PNSP) = penicillin MIC ≥ 0.1 mg/l Penicillin-resistant pneumococci, MIC ≥ 2.0 mg/l PNSP carrying rate = percentage of PNSP of all carrying pneumococci

xviii INTRODUCTION

Infections have been one of the major causes of human disease and suffering throughout history. The introduction of antimicrobials for bacterial infections, beginning in the 1930s, is clearly one of the milestones in the history of modern medicine (Le Fanu 1999). It has been claimed that the use of antimicrobials has added approximately 10 years to human life expectancy in many industrialised countries (McDermott and Rogers 1982). However, bacteria resistant to antimicrobial treatments soon became a worldwide problem, probably partly because of overuse of antimicrobial drugs (Tenover and Hughes 1996; Wise et al. 1998). In contemporary Western societies, infections from the upper respiratory tract are one of the most common reasons for visiting a doctor in primary healthcare (Monto and Ullman 1974). This is especially true regarding upper respiratory tract infections in children (McCaig and Hughes 1995; Söderström 1995; Njalsson et al. 1996; Petursson 1996). Of particular concern in this connection has been the rapid increase of antimicrobial resistance in the bacteria Streptococcus pneumoniae, causing problems in the management of common childhood infections, such as acute otitis media (Klugman 1990; Appelbaum 1992; Neu 1992; Levy 1993; Tomasz 1994; Levy 1998; Dagan 2000). The prevalence of penicillin-resistant pneumococci is highest in countries with relatively unrestricted antimicrobial use. It has been low in northern Europe except Iceland, which is disconcerting as antimicrobial use in Iceland has been relatively restricted (Kristinsson 1995). This thesis is about the use of antimicrobials in children in the community and the possible association of such with the risk of carriage of penicillin-resistant pneumococci, better defined as penicillin-nonsusceptible pneumococci (PNSP). The emphasis is on acute otitis media, which is the main reason for prescribing antimicrobials in children. Furthermore, the spread of one specific PNSP clone over a 10-year period in four well-defined communities in Iceland is examined. Finally, the thesis examines the tympanostomy tube placements as a treatment option for otitis media in association with antimicrobial use. Bacterial resistance to antimicrobials Sulphonamides were introduced for clinical use in the 1930s. Peni- cillin had already been discovered in 1928, but it was not until 1941 that it was first used for the treatment of a patient with a bacterial infection (Fletcher 1984). Penicillin and the other antimicrobials that followed rapidly thereafter were a therapeutic revolution for treatment of lethal infections as well as many chronic and disabling infections. Later, a large number of different antimicrobials were introduced in the market for treatment of bacterial infections. In recent decades, however, the prevalence of human pathogens resistant to antimicrobials has increased rapidly, especially those involved in respiratory tract infections (Levy 1998; Wise et al. 1998; Klugman 2002). The community-acquired bacterial pathogens currently creating one of the biggest antimicrobial resistance problems in respiratory tract infections in the world are PNSP, representing up to 40% of all pneumococcal isolates from infected patients in some parts oft the world (Felmingham 2005). Many of these strains are also multidrug- resistant (resistant to three or more different antimicrobial groups). Of special concern in the last decade is also the increasing prevalence of macrolide-resistant pneumococcus in community-acquired infections. Comparative and analytical studies have demonstrated a relationship between the use of antimicrobials and increase in bacterial resistance to these drugs in the community (Molstad et al 1988; Reichler et al 1992; Arason et al. 1996; Seppala et al. 1997; Melander et al. 2000; Granizo et al. 2000; Arason et al. 2002 a; Bergman et al. 2004; Dias and Caniça 2004; García-Rey et al. 2004; Goossens et al. 2005; Ara- son et al. 2006). Because of the overwhelming threat of antimicrobial resistance in community-acquired infections, partly because of widespread antimicrobial use, the World Health Organisation (WHO) has advised not treating other than established bacterial infections with antimicrobials and using as narrow spectrum of antimicrobials as possible in most instances (WHO 2001). There is much discussion worldwide of how to gather appropriate data regarding antimicrobial resistance. The major problem is getting useful data regarding different study populations, that is, to obtain an accurate picture of resistance on a community level where resistance rates of common pathogens can vary greatly between close areas (Ara- son et al. 1996; Wise and Andrews 1998; Melander et al. 2000; Felm- ingham et al. 2005). Such investigations must therefore be undertaken both nationally and locally, so that meaningful broad-based policies can be devised and relevant clinical guidelines can be developed. It has also been pointed out that there is an increasing need to analyse available data on antimicrobial usage and the prevalence of antimicrobial-resistant organisms in order to help construct mathematical models to use as a tool to predict the likely outcomes of various antibiotic policy options (Wise and Andrews 1998; Austin et al. 1999; Huovinen 2005). These are the main reasons for the study design described in this thesis.

Biochemical processes behind antimicrobial resistance The biochemical process of bacterial resistance to a specific antimicrobial agent results from chromosomal changes, mutation or the exchange of genetic material via plasmid and transposons. Af- ter a resistant clone appears in the community, the resistant clone can spread with selection of resistance, i.e., when most of the fully susceptible bacteria in the population are eliminated, and a resistant sub-population is given the opportunity to proliferate. This is hard to explain except in epidemiological studies, taking into account all possible factors, such as (selective) antimicrobial pressure (antimicrobial use) in the community, changes in use over time and possible herd immunity against this resistant clone, which will be a further topic of the research data in this thesis. The mechanisms by which bacteria protect themselves from antimicrobials can be classified into four basic types (Hawkey 1998): 1) Alterations in the primary site of action like penicillin-binding proteins in pneumococcus. The pneumococcus has at least five different penicillin-binding proteins. Molecular alterations in the primary site of action or in the penicillin-binding proteins in pneumococci may reduce the binding affinity of penicillin to the target as well as for other ß-lactams. 2) Resistant bacteria retain the same sensitive target as antimicrobial-sensitive strains, but the antimicrobial is prevented from reaching it. This happens, for example, with ß-lactamases; the ß-lactamase enzymatically cleaves the four-membered ß-lactam ring, rendering the antibiotic inactive (ß-lactamase-producing bacteria Hae- mophilus influenzae and Moraxella catharralis). 3) Production of an alternative target (usually an enzyme) that is resistant to inhibition by the antimicrobial. 4) Bacteria protect themselves from antimicrobials by preventing the antimicrobial from entering the cell or by pumping it out faster than it can flow in. Bacterial resistance to macrolides can be explained by the two last described pathways.

Streptococcus pneumoniae Streptococcus pneumoniae, usually named pneumococcus is one of the most clinically significant pathogens with emerging antibiotic resistance. It was first isolated by Pasteur in 1881 and has been observed to have been the most common reason for lobar pneumonia, with very high mortality (33%) before antimicrobial treatment was available. After the introduction of sulphonamides, the mortality decreased to 8%, and after the introduction of penicillin, mortality has been very low (Swartz 2002). Pneumococcus, is at present, considered to be the commonest and most important pathogen in acute otitis media, acute sinusitis, pneumonia, septicaemia and meningitis (Musher 1992). The risk, especially of the invasive disease, is higher for children and the elderly (Burman et al. 1985). The main habitat of pneumococcus is the nasopharynx. Pneumococcal carriage is age-related. It increases during the first year of life and is highest in children aged -1 2. Thereafter, carriage rates slowly decline, and adults have much lower rates than children (Gray et al. 1980). Colonised children may transmit pneumococci easily to each other. An essential immunogenic determinant of pneumococci is its capsule made of polysaccharide, which provides protection from phagocytosis. Thus, non-encapsulated strains have less protection and, thereby, have also greatly reduced virulence (Tuomanen et al. 1995; Hall et al. 1996). The antigenicity of the capsule forms the basis for the classification of the 90 known pneumococcal serotypes (Henrichsen 1995; Hall et al. 1996). If sub-typing of the pneumococcus is possible, the number assignment is referred to as a serogroup, e.g., serogroup 6, with subtypes referred to as serotype or subtype 6A, 6B, etc. The host’s protective antibodies are directed against the polysaccharide capsule, and the protection is therefore type-/group- specific, with only slight or no cross-reactivity between antibodies of differing type/serogroup specificity.

Pneumococcae vaccination Vaccination against pneumococci with polysaccharide vaccine has been available on the market since 1977, but the immunogenicity of polysaccharide vaccines, especially among children, is low (King et al. 1996). New protein-polysaccharide conjugate vaccine, including serotypes 4, 6B, 9V, 14, 18C, 19F and 23F, has much higher immunogenicity among children and has been available on the market since 2000 and is part of the routine childhood immunization schedule in the United States (MMWR 2000). Clinical trials have shown efficacy of the vaccine against serotype-specific invasive disease of > 70% (Whitney 2005). Among children under two years of age, the rate of all PNSP invasive diseases has diminished by about 80% in the United States from 1999 to 2004 (Kyaw et al. 2006). Studies evaluating pneumococcal conjugate vaccines effects on nasopharyngeal carriage demonstrate though that vaccination does not impact the overall risk of pneumococcal nasopharyngeal colonization but reduces the acquisition of vaccine-type strains and increases the risk of non-vaccine serotype strain acquisition (O’Brien and Dagan 2003; Veenhoven et al. 2003). The natural balance of microbial species in the nasopharynx might also be altered by pneumococcal vaccination. In studies from the Netherlands, there was a negative correlation for co- colonisation of Staphylococcus aureus and vaccine-type pneumococci, findings suggesting a natural competition between these bacteria, which might also explain an increase in Staphylococcus aureus-related otitis media after vaccination (Bogaert et al. 2004). In Northern California, it has been shown that in those receiving this vaccination there was an 8% reduction in otitis media episodes, a 10% reduction in frequent otitis media and a 24% reduction in tympanostomy tube placements compared with children receiving control vaccine (Fireman et al. 2003). Other studies from the North- America, Israel and Europe (Finland) have also evaluated the effect of pneumococcal conjugate vaccines on clinical or culture-proved pneumococcal otitis media with similar results (Black et al. 2000; Dagan et al. 2001 a; Eskola et al. 2001). Penicillin resistance among pneumococci Most strains of pneumococcus are highly susceptible to both penicillins and cephalosporins but can acquire DNA from other bacteria, that changes the penicillin-binding proteins so that they develop a low affinity for penicillins and hence become resistant to inhibition by penicillins (Tomasz and Munoz 1995). Pneumococcal strains resistant to penicillin and other antimicrobial drugs came on the scene during the late 1960s. The first patient with pneumococcus of decreased sen- sitivity to penicillin was reported from Australia in 1967 (Hansman 1967). However, a high degree of resistance (minimum inhibitory concentration, MIC ≥ 2.0 mg/L) was observed during the late 1970s and, furthermore, multidrug-resistant strains began to appear, with an increasing rate of treatment failures (Appelbaum 1992; Dagan 2000; Felmingham and Gruneberg 2000; Klugman 2002; Swartz 2002). In the literature, penicillin-resistant pneumococci are often defined to include both resistant strains with MIC for penicillin of ≥ 2.0 mg/L, and intermediate-resistant strains with MIC of 0.1-1.0 mg/L. Thus, the choice of antimicrobial group as an empirical treatment of respiratory tract infections from pneumococcus is harder to define now than before throughout the world, but higher doses of traditional agents are sometimes enough to avoid treatment failure if the pathogen is only intermediate-resistant to a given antimicrobial class (Pallares et al. 1995). Today the term penicillin-nonsusceptible pneumococccus (PNSP) is therefore often used for all intermediate- resistant and high-resistant strains together. The first report of PNSP in Iceland came in 1988 (Kristinsson et al 1992). In the following years, 20% of the pneumococcal strains in Iceland isolated from infected patients were PNSP, the majority multiresistant serotype 6B, which was shown to be phenotypically identical by antibiotic susceptibility testing as the Spain6B-2 clone (Soares et al. 1993; Kristinsson 1995).

Otitis media Otitis media continues to be one of the commonest childhood diseases and is a major cause of morbidity in children (Rovers et al. 2004). The pathogenesis is multifactoral, involving the adaptive and native immune system, eustachian-tube dysfunction, viral and bacterial load, and genetic and environmental factors (Bluestone 1996; Rovers et al. 2004). Otitis media with effusion, or ‘glue ear’, may occur as a primary disorder or as a sequel to acute otitis media (Teele et al. 1980). It is very common in children, especially between the ages of one and three years with a time-point prevalence of 10% to 30%, slightly higher during the winter than during the summer (Lous 1995). Bacteria are isolated fairly often in middle-ear exudates, but in spite of this, most patients recover spontaneously (Glasziou et al. 2004). Acute otitis media and otitis media with effusion are different stages of the otitis media continuum. Acute otitis media is defined as the presence of middle-ear effusion in conjunction with rapid onset of one or more signs or symptoms of inflammation/infection in the middle-ear, such as otalgia, otorrhoea, fever, or irritability (Gates et al. 2002). Diagnosis of precise acute otitis media, though, can be hard to define and also differ according to national perspectives and specialty (Rosenfeld 2002). By the age of two, up to 70% of children have had at least one, and every fifth, three or more episodes of acute otitis media in Finland (Alho et al. 1991). Similar incidence has been found in the United States (Teele et al. 1989; Paradise et al. 1997). The high incidence and high rate of spontaneous recovery from otitis media suggest that it is a natural phenomenon, inevitable like the common cold, and play part of the gradual maturation of the child’s immune system. Even though the prevalence of acute otitis media may vary between countries, international rates of antibiotic prescription and surgery for acute otitis media vary greatly, which can largely be explained by the lack of uniform evidence-based guidelines (Schilder et al. 2004). The percentage of patients given antibiotics for acute otitis media varies from 31% in the Netherlands to more than 90% in most other Western countries (Froom et al. 1990; Schilder et al. 2004). Untreated acute otitis media may possibly, though very un- commonly, lead to suppurative complications, such as acute mastoiditis. Even though there are national differences in the incidence of acute mastoiditis, which may possibly be related to prescribing pattern of antibiotics for acute otitis media, the differences are negligible (3.8/100,000 person years for children 14 years and younger in the Netherlands but 1.9/100,000 in United States (Van Zuijlen et al. 2001; Rovers et al. 2004). Initial observation as a treatment strategy seems therefore to be suitable for many children with acute otitis media, but only if appropriate follow-up can be assured. In children younger than two years with a clear clinical picture of acute otitis media, antibiotics are most often advised (Diagnosis and Management of Acute Otitis Media 2004 (The American Academy of Pediatrics and American Academy of Family Physicians guideline); and http:// www.sign.ac.uk/guidelines/fulltext/66/index.html, a national clinical guideline in Scotland (SIGN), last viewed in February 2006). The prediction of recurrent acute otitis media or persistent middle-ear effusion in individual young children remains poor. Young age, childcare outside the home and parental smoking are three of the main risk factors found to significantly increase the occurrence of acute otitis media among children. Other important risk factors in the development of single and recurrent episodes of acute otitis media may include ethnicity, genetic factors, underlying disease, sea- sons and social and economic condition (Uhari et al. 1996; Strachan and Cook 1998; Rovers et al. 2004). Chemoprophylaxis as a specific intervention in the prevention of recurrent acute otitis media, may be more effective than tympanostomy tubes (Casselbrant et al. 1992). In one meta-analysis, antibiotics, appear to have beneficial but limited effect on recurrent otitis media and short-term resolution of otitis media with effusion but no longer-term benefit (Williams et al. 1993). Surgical candidacy depends more on associated symptoms, the child’s developmental risk, and the anticipated chance of timely spontaneous resolution of the effusion. Hearing loss caused by bi- lateral chronic otitis media might lead to behavioural changes and delays in communicative development, although this is still under discussion (Teele et al. 1990; Lous 1995; Rovers et al. 2004; Para- dise et al. 2005). The recommended approach for surgery is to start with tympanostomy tube placement, eventually followed by adenoidectomy. The ideal intervention for chronic or recurrent acute otitis media does though not yet exist, and an urgent need remains to explore new and creative options, based on modern insights into the pathophysiology of otitis media (Rovers et al. 2004). Chronic or recurrent acute otitis media has a considerable negative impact on the quality of life of children and worries their caregivers (Brouwer et al. 2005). The parents of young children hold views on acute otitis media and antibiotics that differ markedly from the medical model in Iceland (Jonsson and Haraldsson 2002). These outcomes should therefore be included in the evaluation of the child with otitis media in both the clinical and research setting.

Acute otitis media and antimicrobial use Acute otitis media is the most common diagnosis (30-65%) leading to antimicrobial prescription for children in the Western world (McCaig and Hughes 1995; Arason et al. 1996; McCaig et al. 2002; Arason et al. 2002 b; Rovers et al. 2004; Arason et al. 2005). Nevertheless, antimicrobial treatment of acute otitis media is debatable. Several randomised clinical trials (Damoiseaux et al. 2000; Little et al. 2001; Le Saux et al. 2005; McCormick et al. 2005) and meta-analyses (Rosen- feld et al. 1994; Del Mar et al. 1997; Takata et al. 2001; Glasziou et al. 2004) indicate that antimicrobial treatment of acute otitis media may often be unnecessary, even for young children. A restrictive antibiotic policy for acute otitis media appears therefore justifiable, and the recent emphasis in Iceland as well as elsewhere has been on watchful waiting for management of children with acute otitis media, especially for those two years and older with mild symptoms or with uncertain diagnoses (see the Icelandic drug guidelines, at http://landlaeknir.is/ template1.asp?PageID=672, last viewed in February 2006). In general, the literature lacks studies comparing antibiotic treatment with placebo administration for acute otitis media and there are no clinical trials using standardised methods for assessing acute otitis media severity. Restrictive policy in antimicrobial use is supported by the documented link between high consumption of antimicrobials and the development of antimicrobial resistance among common pathogens in the community (see chapter “Bacterial resistance to antimicrobials” above). A strong association between antimicrobial use for acute otitis media specifically and carriage of penicillin non-susceptible pneumococci in children has also been demonstrated (Dagan et al. 1998 a; Arason et al. 2002 a; Brook and Gober 2005; McCormick et al. 2005). The increasing rate of resistance to antibiotic drugs is, as a conse- quence, associated with a decrease in the rate of successful eradica- 10 tion of pathogens from middle-ear fluid in acute otitis media, which is associated with clinical failure (Dagan 2000). Further knowledge of the short- and long-term impact of different antimicrobial treatment strategies for acute otitis media is therefore important. Healthcare systems, health-seeking behaviour, and medical management including management, and treatment decision for acute otitis media, differ worldwide. Therefore, when comparing the prevalence of antimicrobial treatments for acute otitis media, it is necessary to adjust for baseline characteristics between countries (Froom et al. 2001). Furthermore, consistency in the treatment pattern within the same practice or healthcare centre in one community is also more likely than that between communities (Diwan et al. 1992; Petursson 1996; Gabbay and le May 2004). Acute otitis media was known to be one of the most common causes of antimicrobial use in children in Iceland when the study was conducted (Bjarnason 1991; Petursson 1996), and pneumococcus is known to be the most common cause, accounting for approximately 50 percent of all cases of acute otitis media (Bluestone 1996; Dowell et al. 1999). One of the most common serotype comprising pneumococcal isolates from middle-ear fluid samples include serotype 6B (Hausdorff et al. 2002). This is the main reason why prescriptions for acute otitis media in different communities and the resistance pattern of pneumococcus are the focus of our studies.

Tympanostomy tube placements Tympanostomy tube placement is a well-established treatment option for chronic effusion in the middle-ear and recurrent episodes of acute otitis media, yet the consequences of this intervention are not always clear (Gates et al. 1987; Franklin and Marck 1998; Rosenfeld 2000; Lous et al. 2005; Paradise et al. 2005; Rovers et al. 2005). Tube otorrhea, often in combination with acute otitis media, is a common and often recurrent and/or stubborn problem in young children who have undergone tube placement for persistent middle-ear effusion (Ah-Tye et al. 2001). No previous data were available about the prevalence of tympanostomy tube among Icelandic children before the present study. This information should also indicate, at least partly, the prevalence of otitis-prone children in Iceland. Even though there are some clinical 11 trials indicating lower antimicrobial treatment frequencies after tube placements (Franklin and Marck 1998), there is a lack of epidemiological studies showing positive effects in diminishing antimicrobial use among children in the community by using tubes on a bigger scale among (all) otitis-prone children. This was one reason to include tympanostomy tube placements in our research.

Background for a study of antimicrobial use in relation to resistant bacteria in Iceland

Sales statistics of antimicrobials Antimicrobials are commonly used, as can be seen from sales statistics. Figure 1 shows the sales of antimicrobials in the five Nordic countries. Based on these figures, the use of antimicrobials is high and had been much higher in Iceland than in the other Nordic countries before the study period. Of special interest was the rapidly increasing use of trimethoprim-sulfamethoxazole (trim-sulfa.) in the early 90s (Fig. 2), which was commonly used for acute otitis media.

DDD/1000 inhabitants/day 25

Iceland 10 Denmark Norway 5 Finland Sweden

0 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Year Fig. 1. Antimicrobial consumption in the Nordic countries based on total sales statistics from the Ministry of Health and Social Security, Iceland, and The Nordic Council on Medicine (data from Denmark do not include hospital usage). 12

DDD/year 35,000 amoxicillin ±clavulanic acid 30,000 penicillin V 25,000 cloxacillin 20,000

15,000 cephalosporin

10,000 trim-sulfa 5,000 macrolides 0 1989 1990 1991 1992 1993 1994 1995 1996 1997

Fig. 2. Total sales of antimicrobial mixtures in Iceland 1989-1997 based on sales statistics from the Ministry of Health and Social Se- curity.

Penicillin-resistant pneumococci in Iceland Another reason for studying the association between the use of antimicrobials and the appearance of antimicrobial-resistant bacteria in Iceland was that a new PNSP appeared in Iceland in the late 1980s, causing clinical problems and a risk of treatment failure, especially when treating children for acute otitis media caused by these pneumococci. The first case of antimicrobial-resistant pneumococcus in Ice- land was observed in 1988 and in the next years proved to be mainly a multiresistant serotype 6B strain (Kristinsson et al. 1992), probably coming from Spain, where this tribe, now registered as Spain6B-2, had previously been observed (Soares et al. 1993). Later on it was shown that the prevalence of this particular strain (clone) increased rapidly in Iceland (Vilhelmsson et al. 2000; Sa-Leao et al. 2002). When this study started, cultivation of bacterial sampling from hospital series indicated a PNSP prevalence rate of about 20%, almost all of them being multiresistant serotype 6B (Kristinsson 1995). The prevalence in the community was at that time not known. 13 It has been previously pointed out, that there has been lack of population studies, based on studies of both accurate antimicrobial sales statistics and antimicrobial resistance in the community (Wise and Andrews 1998; Felmingham et al. 2005). A study of antimicrobial consumption and antimicrobial resistance in Iceland was therefore considered propitious for several reasons: • The study could be carried out in well-defined geographical areas. • Computerised medical records were available and had been used for several years. • Computerised sales records for drug sales were available from the pharmacies. • Areas could be studied where there was only a single primary healthcare centre in each community, to which the vast majority of subjects with upper respiratory tract infections turned. • The personnel working at the primary healthcare centres are stable. • The GPs have an international view, as the vast majority of Icelandic GPs have been educated abroad in different parts of the world. 14 RESEARCH QUESTION AND AIM OF THE STUDY

Main research question The main question of this study was the potential association between the use of antimicrobials outside hospitals and the development and spread of antimicrobial-resistant bacteria, mainly Strepto- coccus pneumoniae, in the community (Fig. 3).

Antimicrobial use Antimicrobial resistance in the community in the community

Fig. 3. Main research question of the thesis.

As mentioned above, one of the most common reasons for prescribing an antimicrobial is middle-ear infection (acute otitis media) in children. This was a reason to confine our 1998 and 2003 studies (phase II and III) to pre-school children, 1-6 years of age, and to include the occurrence of acute otitis media as a main reason for antimicrobial usage and use of tympanostomy tubes as a well-established treatment option for recurrent episodes of acute otitis media, in the study plan. Most pre-school children one year of age or older (about 80%), are enrolled at day-care centres and were therefore easily available for possible participation. Figure 4 includes the main potential associations being focused on in our studies.

Aim of the study In summary, the overall aim was to analyse the use of antimicrobials and the reasons (main diagnosis) for prescribing antimicrobials, on one hand, and carriage of penicillin-nonsusceptible pneumococci (PNSP), on the other, in pre-school children in Iceland. 15

Acute otitis media

Antimicrobial resistance development Antimicrobial among use pneumococci (spread/ selection)

Tympanostomy tube placement

Fig. 4. Hypothesised associations between the main factors studied in this thesis.

Specific aims • To describe the total use of antimicrobials in the communities, specifically among pre-school children, by class of antimicrobials, amount prescribed and prescription rate in selected, well-defined communities.

• To describe potential links between antimicrobial treatment for acute otitis media, socio-demographic factors and parental views on the use of antimicrobials.

• To describe the use of tympanostomy tube placements and possible association with the use of antimicrobials among children.

• To analyse associations between antimicrobial use and nasopharyngeal carriage of PNSP in children with regard to both individual use and total use in the community.

• To describe clonal spread of PNSP in communities and to analyse the interplay of factors contributing to this spread. 16 STUDY POPULATIONS

Demography of Iceland Iceland is a volcanic island in the North Atlantic Ocean (Fig. 5), just south of the Arctic Circle, with an area of 103,000 km2 and 299,891 inhabitants at the end of 2005. The population is limited to a narrow coastal belt, and most of the people live in and around the capital, Reykjavik, on the south-west coast. Beginning in the Caribbean and ending in the North Atlantic, the Gulf Stream plays an important role in the pole-ward transfer of heat and salt surrounding Iceland. The climate is characterised by a relatively small difference in temperature between summer and winter, an oceanic climate.

Fig. 5. The North-Atlantic countries.

Characteristics of the study areas This thesis is based on studies from five areas (Fig. 6). These are Hafnarfjordur and Gardabaer (HG, when both communities represent one study area with a common off-hours service in phase I, but H, when Hafnarfjordur alone represented the same study area in 17

Fig. 6. Study areas in Iceland. phases II and III), Vestmannaeyjar (V), Egilsstadir (E), Bolungarvik (B) and Hella and Hvolsvollur (HH, only included in phase I). Hafnarfjordur (H) and the smaller neighbour town Gardabaer (G) are adjacent to the capital Reykjavik. The town of Vestmannaeyjar (V) is a fishing centre on an island off the south coast. Egilsstadir (E) in East Iceland, and the smaller town Hella/Hvolsvollur (HH) in the southern part are surrounded by large farming areas. Bolungarvik (B) is a small fishing town in north-west of Iceland. The climate in Vestmannaeyjar (V) is described as somewhat warmer and wind- ier than in other parts of Iceland, whereas Egilsstadir (E) is more characterised by a climate closer to some parts of Scandinavia, with colder winters, less humidity and warmer summers than elsewhere in Iceland. Classical weather parameters for the study areas as well as the years of the three phases during the 10-year period are shown in Table 1 (The Icelandic Meteorological Office http://www.vedur. is, last viewed February 2006). The weather parameters shown did not differ much between the research areas during the study period, except for more mean wind speed in Vestmannaeyjar than observed in the other study areas. 18

Table 1. Temperature, humidity and wind speed during the years 1993, 1998 and 2003 in four research areas in Iceland; Hafnarfjordur (H), Vestmannaeyjar (V), Egilsstadir (E) and Bolungarvik (B) (ND = no data available). Area Year Temperature, degrees Celsius. Relative Mean wind Mean (range) humidity speed. Me- tres/second January July Jan. July Jan. July H1 1993 -2.3 (-12.7 to 6.8) 10.1 (4.7 to 19.7) 76.9 75.0 6.7 4.6 1998 0.6 (-13.7to 8.8) 11.1 (5.4 to 18.0) 73.8 78.9 5.7 3.8 2003 1.5 (-11.3 to 9.1) 12.3 (6.8 to 18.7) 76.7 79.5 4.7 2.6 V2 1993 -0.2 (-12.2 to 7.2) 9.3 (4.8 to 15.9) 76.2 80.2 13.0 9.0 1998 2.6 (-9.3 to 7.7) 10.4 (6.4 to 17.0) 77.6 88.3 9.4 6.6 2003 3.1 (-4.4 to 8.2) 11.4 (7.1 to 20.0) 79.8 88.6 12.9 7.5 E 1993 -4.5 (-18.6 to10.0) 7.5 (3.5 to 14.5) 89.5 86.6 6.6 5.2 19983 -1.1 (-18.8 to 8.4) 8.4 (-0.9 to 25.2) 90.1 ND 6.7 ND 20033 -2.7 (-19.9 to 7.2) 11.1 (2.5 to 22.1) ND ND ND ND B 19934 -3.2 (-17.0 to 7.1) 7.0 (3.3 to 15.2) 73.6 84.7 7.7 5.0 1998 -0.3 (-11.2 to 8.0) 8.8 (2.5 to 17.0) 79.4 79.1 7.9 3.8 2003 1.0 (-7.9 to 9.2) 10.3 (3.5 to 18.0) 78.8 80.7 5.7 4.4 1Reykjavík station, 2Stórhöfdi station (on Heimaey, Vestmannaeyjar), 3Egilsstada airport in July 1998 and 2003, 4Galtarviti station (15 km from Bolungarvík) in 1993.

Choice of study areas The reasons for selecting study areas vary. They were selected to represent rural (B, E, HH and V) and urban (H, HG) areas. These areas are also geographically well-defined, evenly distributed around the country and have reliable registers of all inhabitants, based on the National Register “Statistics Iceland” (http://hagstofan.is/, last viewed in February, 2006). The primary healthcare centres in areas H, B and E had well-established teaching practices, and the content of care in these practices had also been well documented from previous research (Sigurdsson et al. 1989; Njalsson et al. 1996; Halldorsson et al. 2002; Petursson 2005 a ). The five study areas corresponded to seven communities, each served by one primary healthcare centre, where GPs and other staff are responsible for all primary healthcare, including on-call services night and day, throughout the year. The medical records in all these primary healthcare centres have long been computerised. The 19 healthcare centre in area H was the author’s own workplace during all phases of this study. This study is an epidemiologic cross-sectional follow-up study. In analyses of individuals (randomised trials), the basic assumption is that there are no connections between the outcome for one person and that of any other person (Campell et al. 1999). When analysing GPs prescription habits or practices, it is more likely that the outcome for many patients will have a similar pattern if they are treated by the one and the same physician. Furthermore, it is more likely that there is a consistent treatment pattern within the same practice or healthcare centre than between practices and healthcare centres (Diwan et al. 1992; Gabbay and le May 2004; Petursson 2005 a). The study areas were therefore feasible to examine differences in medical praxis in the primary healthcare in Iceland in connection with antimicrobial prescription habits.

Organisational structure of the healthcare service The main organisational structure of the healthcare service was by and large similar during the 10-year study period. There is direct access to all doctors in Iceland, and GPs therefore have no gate-keep- ing role as they do in some other countries. The same otolaryngology specialist visited areas V, E and B bi-monthly during the years 1998 and 2003, a fact which may be taken into consideration when dealing with the results described in Papers III and IV. The study areas were served by a total of 19 GPs (18.2 positions) in 2003, of whom 11 were the same individuals as in the 1998 study, and 8 were the same individuals as in the 1993 study. As areas H and G are suburbs of the capital Reykjavik, the inhabitants in these areas had easy access to their GPs as well as to other specialists in Reykjavik. In this respect there was no change for H during the study period. However, some other changes took place in area H that may have affected the results of our study. After phase II, off-hours service for children was provided more often outside the H area, resulting in some decline in the continuity of care in area H and, consequently, probably some underestimation of antimicrobial prescribing.

Details on data collection from the different areas The cross-sectional investigations were carried out in three phases: 1992- 20 1993, 1997-1998 and 2003. Sales statistics over 12 months, based on computerised data on prescriptions from the local pharmacies were collected separately in the first phase from October 1992 to September 1993 and in the second phase from May 1997 to April 1998. No prescription data on sales statistics were collected during the third phase of the study. In the first phase, nasopharyngeal specimens were collected from October 1992 to November 1993, excluding the months of June, July and August. In phases II and III the collection was made during the months March to May in 1998 and 2003, respectively, as was the administration of questionnaires. In the third phase, otoscopy was performed if the child’s records indicated tympanostomy tubes. As most contacts with the participants in 1992-1993 were made in 1993 (~90%), and all contacts in the second and third phases were made in 1998 and 2003, the three phases will hereafter be referred to as the 1993, 1998 and 2003 studies, respectively. Three communities Gardabaer (G) (population 7,493) and Hella and Hvolsvollur (HH) (population 3,150), were only included in the 1993 study (I). This means that the cross-sectional follow-up includes four well-defined communities: Hafnarfjordur (H), Vestman- naeyjar (V), Egilsstadir (E) and Bolungarvik (B). Gardabaer (G) was excluded from the 1998 and 2003 studies for practical reasons, and Hella and Hvolsvollur (HH) because no data from the local pharmacy could be obtained in 1992-1993. An overview of the study population and participation is given in Table 2.

Selection criteria for the study groups In all phases of the study, children receiving antimicrobials in the preceding two weeks were excluded as far as the analysis of nasopharyngeal specimen sampling was concerned, as shown in Tables 2 and 3. The 1993 study (I) referred mainly to children up to seven years of age (thus also including those less than one year of age) who were visited at day care centres on given days or went to the primary healthcare centres to visit a doctor for vaccination or because of an acute, unspecified upper respiratory infection (common cold), while the 1998 studies (II-III) and those in 2003 (IV-V) were supposed to include children representative of all 1- 6 years old children living in the study areas. In the 1998 studies (II, III), there was a computerised 21

Table 2. Study population from phases II (1998) and III (2003) and, for comparison, from phase I (1993), where children from area HH and children <1 year of age were excluded from the results presented in Paper I. In the table a) includes the total sample, and b) excludes those who had been treated with antimicrobials during the last two weeks, and for whom no nasopharyngeal sampling was analysed. Area and year Population Children Invited Participated 1-6 years (% of invited) old N (number) N % N % N % Mean age±SD Hafnarfjördur (area H) 19931 25452 2670 11 527 3.6±1.5 1998, b) Paper II 18203 1989 11 401 20 301 75 4.2±1.8 1998, a) Paper III 18203 1989 11 442 22 331 75 4.1±1.8 2003, a) Paper IV 20675 2004 10 380 19 287 76 4.2±1.7 2003, b) Paper V 20675 2004 10 351 18 258 74 4.2±1.7 Vestmannaeyjar (area V) 1993 4883 529 11 100 4.6±1.0 1998, b) Paper II 4640 512 11 295 58 224 76 4.2±1.7 1998, a) Paper III 4640 512 11 321 63 244 76 4.2±1.7 2003, a) Paper IV 4416 406 9 396 98 324 82 4.4±1.6 2003, b) Paper V 4416 406 9 373 92 301 81 4.2±1.6 Egilsstadir (area E) 1993 3071 318 10 111 3.8±1.5 1998, b) Paper II 3076 300 10 190 63 167 88 4.0±1.8 1998, a) Paper III 3076 300 10 198 66 174 88 4.1±1.8 2003, a) Paper IV 2874 265 9 256 97 216 84 4.2±1.7 2003, b) Paper V 2874 265 9 247 93 207 84 4.2±1.7 Bolungarvik (area B) 1993 1176 123 11 53 3.8±1.5 1998, b) Paper II 1094 99 9 62 63 51 83 4.2±1.7 1998, a) Paper III 1094 99 9 66 67 55 83 4.2±1.7 2003, a) Paper IV 957 82 9 75 92 62 83 3.9±1.6 2003, b) Paper V 957 82 9 71 87 58 82 3.9±1.6 1Hafnarfjördur together with Gardabaer in the 1993 study 22

Table 3. Details on data collection from the different areas. Study Study Paper Type of data Areas Ages population year number Prescription data HG (1993), All ages 34,582 1993 I from pharmacies H (1998), V, 27,013 1998 II E, and B Prescription data HG (1993), 0-6 years 9191 1993 I from parents and H (1998, 1-6 years 804 (743) 1998 III (II) medical records 2003), V, E, 1-6 years 889 (824) 2003 IV (V) and B, HH (only 1993) Data from naso- HG (1993), 0-6 years 9191 1993 I pharyngeal bacteria H (1998, 1-6 years 743 1998 II sampling 2003), V, E, 1-6 years 824 2003 V and B, HH (only 1993) Data from ques- H, V, E, B 1-6 years 804 1998 III tionnaire on paren- 1-6 years 889 2003 IV tal view Data on acute otitis H, V, E, B 1-6 years 804 1998 III media and tympa- 1-6 years 889 2003 IV nostomy tubes 1Of these, 791 children were 1-6 years old when area HH was excluded; they were therefore comparable in age to the children studied in phases II and III in 1998 and 2003 (see Table 2.). random sample comprising children, 1-6 years of age from all the study areas; it was drawn from the National Registry, “Statistics Ice- land”, while in 2003 the sample was a random sample of children, 1- 6 years old, from Hafnarfjordur and including all available children of those ages from the other areas.

Overview of the data presented in the thesis Table 3 summaries the different sources of data presented in this thesis. Table 2 gives an overview of the study areas, ages and numbers of participants in the three examination phases described in the different Papers. The lower number of the participants in Tables 2 and 3, representing Papers II and V is due to the exclusion of 61 children from the nasopharyngeal bacteria sampling because of antimicrobial treatment during the preceding 14 days in the 1998 study, and 65 children being excluded from the 2003 study for the same reason. 23 METHODS

Antimicrobial sales statistics In the 1993 and 1998 studies (I, II) computerised information on total sales of oral antimicrobials prescribed during one year for all inhabitants, adults as well as children, was collected from the local pharmacies (not hospital use) in the four areas HG (1993), H (1998), V, E and B. No data on prescriptions were available from the local pharmacy in area HH. Numbers of defined daily doses (DDD) were calculated per 1000 inhabitants per day (WHO 1992).

Microbiology and nasopharyngeal sampling for pneumococci Nasopharyngeal samples were obtained with rayon tipped swabs and stored for a maximum of 48 hours until being processed in the microbiology laboratory of the University Hospital. They were then inoculated on blood and chocolate-blood agar and incubated aerobically and anaerobically in 1993 and 1998, but only anaerobically in 2003. Pneumococci were identified by conventional methods and screened for penicillin resistance by the oxacillin disc diffusion test according the Kirby-Bauer method 1993 (Ruoff 1995; Woods and Washington 1995) and according to the NCCLS method and criteria in the studies performed in 1998 and 2003 (Jorgensen et al.1999). The minimal inhibitory concentration was determined by the agar dilution method 1993 (Woods and Washington 1995) and by E-test (Tenover et al. 1996) in 1998 and 2003, according to the manufacturer’s recommendations (AB Biodisk, Solna, Sweden). The pneumococci colonies were also screened for susceptibility to tetracycline, erythromycin, chloramphenicol and trimethoprim-sulfamethexazole. In 2003 clindamycin was added to this screening procedure. Penicillin non-susceptible isolates were also serotyped by co-agglutination (Kronvall 1973) using antisera from the State Serumin- stitute (Copenhagen, Denmark). Further details about the identification of bacteria, the screening for antimicrobial resistance, laboratory methods and standards are given in Papers I, II and V. 24 Information about infectious disease history and socio-demographic factors In the 1993 study (I) parents completed a questionnaire. The questionnaire included questions about demographic factors, the number of children in the household, whether the children were enrolled in a day care centre, the number of oral antimicrobial prescriptions during the preceding year, including not only prescriptions made by their GP´s but also those made by other specialists, the date and name of the last antimicrobial agent, type of infection and whether the child had been taking prophylactic antimicrobials for three weeks or more in the preceding year. The information collected from parents was matched with that available from the medical records at the local healthcare centre. Parental information was used when medical records could not be traced, especially when children had been seen by other professionals outside the study areas (around 5% of the cases). In the 1998 and 2003 studies the parents of the participating children received postal questionnaires, asking the same questions as in the 1993 study, with additional questions about both past and present use of tympanostomy tubes. In 2003, there were also additional questions about smoking in the household. Parents were also asked to complete a questionnaire about their personal preferences regarding antimicrobial treatment in the case of 1) unspecified upper respiratory infections (common cold) and 2) acute otitis media. Parents answered the question whether it was always, sometimes or never appropriate to give antimicrobials in these two situations, or whether they did not know. They were then asked to agree, disagree or give no comment (or answer “do not know”) to the following two statements; “Some pathogens are becoming resistant to antimicrobials” and “Inappropriate antimicrobial use can lead to antimicrobial resistance problems with common pathogens”.

Statistical methods Carriage of penicillin-nonsusceptible or penicillin-susceptible pneumococci was the most important single outcome variable in Papers I, II and V. Carriage of erythromycin-resistant pneumococci or erythromycin-susceptible pneumococci was also an outcome variable in Paper V. Antimicrobial treatment or not for acute otitis media and 25 the presence or history of tympanostomy tube placements or not were the outcome variables in Papers III and IV. Recent (< 8 weeks) antimicrobial use for acute otitis media or not for children having tympanostomy tubes or not, adjusted for age, were also outcome variables in Papers III and IV. The Pearson chi-square test or Fisher´s exact test was used for univariate analysis of categorical variables and one-way ANOVA for continuous variables. The multivariate logistic regression method was used to estimate the risk for all variables potentially contributing to antimicrobial resistance (I, II and V), antimicrobial treatment for acute otitis media (III, IV), presence of tympanostomy tube(s) (III, IV), and parental willingness to accept antimicrobial treatment for the common cold (III) in order to control interdependence. Indi- vidual regression coefficients were tested with the Wald statistic, and confidence intervals were calculated for the odds. All analyses were performed with the SPSS® program for Windows (Advanced Statis- tics Release 6.0 (1993) and 8.0 (1998 and 2003) SPSS Inc, Chicago, IL). Linear regression analysis was used to estimate correlation coefficient (r), and the 95% confidence interval for the slope of the mean number of antimicrobial courses for acute otitis media compared to the tympanostomy tube placement rate (cumulative rate) by areas (IV). Linear regression analysis was also used to estimate the correlation between the mean number of total antimicrobial courses and the prevalence of parents finding it appropriate to sometimes treat common colds with antimicrobials (IV). The level of statistical significance was set at 0.05, and 95% confidence intervals were given. Further information about statistical methods is given in the separate Papers, I-V. Statistical assistance was provided by Júlíus Björnsson and Örn Ólafsson, Landspitali University Hospital, Reykjavik.

Ethical considerations The 1993 study was approved by the Ethics Committee of the Direc- torate of Health. The 1998 and 2003 studies were approved by the National Bioethics Committee and National Data Protection Com- mission, Iceland. Data on individuals were only collected if the parents had given consent for the participation of their children. 26 RESULTS

Sales statistics for antimicrobial use in communities (I, II) The total antimicrobial use during one year in the communities, including all ages, was gathered in the 1993 and 1998 studies. A total of 22,132 prescriptions were dispensed by local pharmacies in the 1993 and 15,153 in 1998. The calculated amount used in terms of the number of defined daily doses (DDD) per 1000 inhabitants per day is shown in Table 4.

Table 4. Antimicrobial use 1993 and 1998 according to sales statistics, measured as the number of defined daily doses (DDD) per 1000 inhabitants per day in the study areas. Number of DDD/1000/day Study area 1993 1998 H 13.61 14.2 V 19.9 17.2 E 16.7 12.3 B 13.6 11.2 1Together with Gardabaer in the 1993 study

Antimicrobial sales according to age, gender and time of year (1997-1998) When antimicrobial use is analysed as the rate of prescriptions in the 1998 study (Fig. 7), the highest incidence of prescriptions is among pre-school children. Women used more antimicrobials than men and, as shown in Figs. 7 and 8. Most antimicrobial use was during the winter (Fig. 8).

Fig. 7. Incidence of antimicrobial prescriptions by age and gender in the 1998 study (information from annual drug-store sales statistics).

Fig. 8. Antimicrobial use as number of defined antimicrobial doses (DDD) per 1000 inhabitants per day by gender and month in the 1998 study (information from annual drug-store sales statistics). 27

Number of antimicrobial prescriptions per inhabitant per year 1.4

Men 1.2 Women 1.0

0.8

0.6

0.4

0.2

0.0 85+ 0 to 4 0 to 9 5 to 10 to 14 10 to 19 15 to 24 20 to 29 25 to 34 30 to 39 35 to 44 40 to 49 45 to 54 50 to 59 55 to 64 60 to 69 65 to 74 70 to 79 75 to 84 80 to Age groups Fig.7 (above) and Fig. 8 (below). See text on opposite page.

DDD/1000 inhabitants/day 25

10 Men

5 Women

0 Jan Oct Feb Sep Dec July Nov May June April March August 28 Type of antimicrobial drug sales (1997-1998) The types of drugs prescribed varied according to age. In the youngest age group, amoxicillin and amoxicillin plus clavulanic acid were the most common drugs used, whereas tetracycline dominated in the teenage groups (Fig. 9). No big difference was observed between areas in the 1997-1998 study when types were analysed as a percentage of all antimicrobials prescribed. No difference was observed by gender and the type of drug prescribed.

Changes in antimicrobial sales for children between 1993 and 1998 In Paper II, antimicrobial sales for children < 7 years old between 1992-1993 (6,223 prescriptions) (I) and 1997-1998 (3,347 prescriptions) were compared for each area studied. The number of defined daily doses/1000 children/day and the number defined daily doses per prescription were calculated, for both the total use and each antimicrobial group specifically. Antimicrobial use had diminished in DDD/1000 inhabitants/day 9 9 8 0-6 years old 8 7-13 years old 7 7 6 6 5 5 4 4 3 3 2 2 tetra- 1 1 cycline 0 0 penicillin V 9 9 8 14-20 years old 8 21 years and older amoxicillin± 7 7 clavulanic acid 6 6 trim-sulfa 5 5 4 4 3 macro- 3 lides 2 2 others 1 1 0 0 Fig. 9. Antimicrobial use according to age groups in the study areas 1997-1998 (information from annual drug-store sales statistics). 29 all study areas in terms of both as number of defined daily doses (14- 43%) and the number of antimicrobial treatment courses per year (9-50%). The reduction in antimicrobial use was greater for trimethoprim-sulfamethoxazole than for other antimicrobials, in one area (area V) dramatically or from 7.1 to 1.4 DDD/1000 children/day (II) (see also Fig. 2). Overall, there was no change in the number of defined daily doses per prescription between these two periods (II).

Antimicrobial use among pre-school children in the sampled groups (I, III, IV) The use of antimicrobials was commonest in the youngest children, as shown in Figure 10. The use was statistically lower in 1998, 1.21 antimicrobial treatments per child per year (95% CI 1.09-1.32) and 2003, 1.06 (0.95-1.17) than during the first study period, 1993, 1.51 (1.39-1.63) but the difference between children of the same age was similar in the three studies. Although the number of antimicrobial courses prescribed for pre- school children per year, as observed in the sampled children 1-6 years

Number 3.0

2.5 1993 1998 2.0 2003

1.5

1.0

0.5

0.0 1 2 3 4 5 6 Age in years Fig. 10. Yearly incidence of antimicrobial treatments per child in relation to age in 1993, 1998 and 2003. 30

Hafnarfjordur Egilsstadir 2.5 2.5 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0.0 0.0 1993 1998 2003 1993 1998 2003 These graphs show the number of antimicrobial treatments/child/year Vestmannaeyjar Bolungarvik 2.5 2.5 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0.0 0.0 1993 1998 2003 1993 1998 2003

Fig. 11. Yearly incidence of antimicrobials among children 1-6 years of age in different study areas in the 1993, 1998 and 2003 studies. of age, diminished during the 10-year period by about one third, it varied between study areas (Fig. 11). This time trend was of statistical significance for all areas except for Vestmannaeyjar (area V). Amoxicillin was most commonly the last antimicrobial drug prescribed before children entered the study in all three studies (1993, 1998 and 2003), as shown in Figure 12. In the 1993 study, the use of trimethoprim-sulfamethoxazole was common (I) but diminished dramatically in the 1998 study (II) and further still in the 2003 study (V), as also shown in Figure 2 (Total sales of antimicrobial mixtures in Iceland 1989-1997, based on sales statistics from the Ministry of Health and Social Security). The choice of antimicrobial drugs also varied considerably by study area. In 2003, broad-spectrum antimicrobials (amoxicillin+clavulanic acid, azithromyzin, erythromycin, trimethoprim-sulphamethoxazole) were used in only 23 out of 72 cases (32%) in area E, where the total antimicrobial consumption was lowest, compared with 148 out of 189 cases (78%) in the high- 31

1993 1998 2003 2% 6% 2% 2% 16% 23% 2% 4% 35% 5% 7% 4% 25%

9% 36% 37% 50% 26% 9%

penicillin V amoxicillin amoxicillin + clavulanic acid macrolides trim.-sulfa. Other azithromyzin

Fig. 12. Choice of last antimicrobial group prescribed before study entry among 1-6 year old children in the 1993, 1998 and 2003 studies. consumption area V (p<0.0001) (IV). In 2003 a new antimicrobial, azithromycin, had been introduced in the market. This was used more in area V (33.3%) than in the other areas and almost not at all in the area E (1.5%) (V).

Main diagnoses when prescribing antimicrobials for children Figure 13 shows the main reasons for prescribing antimicrobials for children 1-6 years of age just before their entry into the study when participating in the 1993, 1998 and 2003 studies. As seen in the figure, acute otitis media was by far the commonest reason in all three studies, followed by tonsillitis. Very few children were prescribed antimicrobials for sinusitis in the 1993 study, while this percentage was 10% and 12% in the studies in 1998 and 2003, respectively.

Antimicrobial use for acute otitis media Figure 14 shows the percentage of children receiving antimicrobial treatment for a diagnosis of acute otitis media in the previous 12 months (yearly prevalence) by age in the three studies. Antimicrobial 32

1993 1998 2003 1% 3% 5% 1993 3% 3% 7% 3% 7% 8% 3% 7% 7% 8% 17% 10% 12%

17% 10% 65% 51% 53%

acute otitis media tonsillitis sinusitis pneumonia bronchitis acuta cutaneous infections urinary tract infections Fig. 13. Main last diagnosis when prescribing antimicrobials for children, aged 1-6, in the 1993, 1998 and 2003 studies.

Percentage 80%

70% 1993

60% 1998

50% 2003

40%

30%

20%

10%

0% 1 2 3 4 5 6 Age in years

Fig. 14. Yearly prevalence as the percentage of children receiving antimicrobial treatment for acute otitis media by age and study year. 33 treatment was more common in the lower ages studied, 54% (95% CI 44-64%) for one-year-old children in the 2003 study. The yearly prevalence was statistically lower in the 1998 study for children 1-6 years old, 35% (95% CI 31-38%) and in the 2003 study, 31% (95% CI 28-34%) compared with the 1993 study, 48% (95% CI 45-52%). Figure 15 shows the number of treatments for acute otitis media in the previous year by age (yearly incidence). The results are in agreement with those shown in Figure 10. Over the study period, the yearly incidence of antimicrobial treatment because of acute otitis media decreased from 1.02 (95% CI 0.92-1.12) in the 1993 study to 0.70 (95% CI 0.61-0.79) in the 1998 study and further but not significantly, down to 0.60 (95% CI 0.52- 0.68) in the 2003 study. In the 2003 study, the incidence was highest for two-year-old children, 1.35 (95% CI 1.03-1.68), 1.27 (95% CI 0.93-1.61) for one-year-old children, 0.65 (95% CI 0.50-0.80) for tree-year-olds, 0.37 (95% CI 0.26-0.47) for four-year-olds, 0.20

Number/child/year 2.5

2.0 1993

1998 1.5 2003

1.0

0.5

0.0 1 2 3 4 5 6 Age in years

Fig. 15. Yearly incidence of antimicrobial treatment for acute otitis media per child in relation to age and study year. 34

Hafnarfjordur Egilsstadir 1.6 1.6 1.4 1.4 1.2 1.2 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 1993 1998 2003 1993 1998 2003 These graphs show the number of antimicrobial treatments for AOM/child/year Vestmannaeyjar Bolungarvik 1.6 1.6 1.4 1.4 1.2 1.2 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 1993 1998 2003 1993 1998 2003

Fig. 16. Yearly incidence (95% confidence interval) of antimicrobial treatment for acute otitis media per child in different areas studied in 1993, 1998 and 2003.

(95% CI 0.11-0.28) for five-year-olds and 0.14 (95% CI 0.07-0.21) for six-year-old children. Figure 16 shows the number of treatments for acute otitis media during the preceding year in the three studies in the different areas. Similarly to what was shown in Figure 11, there was a significant decrease in all the areas except for Vestman- naeyjar (area V).

Predictors for antimicrobial prescribing for acute otitis media The child’s age (younger age), history of tympanostomy tubes (past or present) and residence in area V, were independently associated with the number of antimicrobial treatments for acute otitis media (IV). In the 1998 study (III), this was the case only for younger age. Smoking in the family household did not influence the odds for whether children received antimicrobials for acute otitis media or not in the 2003 study. 35 Association between parental expectations and doctor’s prescription habits for management of upper respiratory tract infections in children In both the 1998 and 2003 studies (III, IV), the vast majority of parents (80-90%) in all areas agreed to the following two statements: “Some pathogens are becoming resistant to antimicrobials” and “In- appropriate antimicrobial use can lead to antimicrobial resistance problems with common pathogens”. Table 5 shows the results of the questionnaires about what the parents considered appropriate antimicrobial usage for the common cold and for acute otitis media in the total number of participants in the 1998 (III) and 2003 (IV) studies.

Table 5. Parents’ views on appropriate antimicrobial treatment as reported in questionnaires from the 1998 and 2003 studies (percentage in brackets). Year Always Sometimes Never Don’t know Is it appropriate to give antimicrobial treatment for unspecified upper respiratory tract infections (common cold)? 1998 1 (0.1) 346 (43.4) 377 (47.3) 73 (9.2) 2003 0 (0) 394 (45.0) 420 (48.2) 59 (6.8) Is it appropriate to give antimicrobial treatment for acute otitis media? 1998 66 (8.3) 686 (86.0) 13 (1.5) 33 (4.1) 2003 75 (8.5) 757 (86.3) 6 (0.7) 39 (4.4)

The vast majority of parents in all the areas were also of the opinion that acute otitis media should only sometimes be treated with antimicrobials. Very few stated that antimicrobial treatment was always indicated for treating a common cold, while a similar percentage of parents stated “sometimes” and “never”. At the community level (IV), a significant correlation was found between the children’s total use of antimicrobials and the percentage of parents considering it sometimes appropriate to treat a common cold with antimicrobials (r = 0.99, p = 0.01). In area E, where the prescription rate was lowest, it was also commonest for the parents to state that antimicrobial treatment was never necessary for treatment of a common cold, both 1998 and 2003 (III, IV). The response from parents to the questionnaire addressing issues of parental expectations and aware- 36 ness, further indicated that parents who consider it inappropriate to treat unspecified upper respiratory tract infections with antimicrobials significantly more often preferred that acute otitis media not be treated with antibiotics (III). They also more often considered it appropriate to prescribe antimicrobials for unspecific upper respiratory tract infection if their child had previously received antibiotics for acute otitis media (III).

Tympanostomy tube placements (III, IV) Figure 17 shows the cumulative prevalence of being subjected to tympanostomy tube insertion as reported in the 1998 and 2003 studies. About one third of the children had tympanostomy tube(s) currently or earlier. The curves for cumulative prevalence of tympanostomy tubes during the first six years were similar in the 1998 and 2003 studies. From 1998 to 2003 there was an increase in tympanostomy tube

Percentage 50%

45%

40%

35%

30%

25%

20%

15% __ __ 1998

10% _____ 2003

0% 0 1 2 3 4 5 6 Age in years Fig. 17. Cumulative prevalence as a percentage (95% confidence interval) of use of tympanostomy tubes 1998 and 2003 among 1-6 years old children in the study areas. 37 placements in areas V (34.8 to 44.1%, p=0.034) and H (26.1 to 36.8%, p=0.006), where antimicrobial prescription rates were highest, and a decrease in areas E (26.4 to 17.2%, p=0.049) and B (34.0 to 24.6%, p=0.299), where the antimicrobial rates were lowest. In area E antimicrobial use had also diminished significantly (IV). Table 6 shows the odds ratio for having tympanostomy tube(s), compared with those not having tympanostomy tube(s) for various variables studied. Odds ratios were significantly higher for residents of area V versus area E, day care attendance, and treatment with antimicrobials for acute otitis media, but not for gender or smoking in the family household (IV).

Table 6. Odds ratio by multivariate analysis, adjusted for age, for children 1-6 years old having tympanostomy tube(s) at present (n=123) as opposed to not having tube(s) (n=736) in the 2003 study. Variable No. Odds ratio 95% CI p-value Residence Area V 314 1 Area E 214 0.35 0.17-0.64 0.0021 Area B 61 1.02 0.46-2.24 0.97 Area H 270 0.81 0.50-1.30 0.38 Gender Female 407 1 Male 452 1.28 0.84-1.94 0.25 Day care No 71 1 Yes 788 2.38 1.07-1.72 0.0317 Smoking in the family household No 701 1 Yes 158 1.01 0.60-1.72 0.95 Number of antimicrobial treatments for acute otitis media during the last 12 months 0 594 1 1-2 203 1.96 1.22-3.17 0.0059 >3 62 4.98 2.60-9.53 0.0001 Multivariate analysis (859 cases analysed, data missing in 30 cases) Overall significance: chi-square = 100.176, df = 9, p < 0.0001 38 Association between tympanostomy tube placements and antimicrobial use Based on analyses by individuals, there was an association between having at present tympanostomy tube(s) and antimicrobial use because of acute otitis media in the last 12 months among children 1-6 years old, as observed when studying these two factors in the 2003 study (Table 6) (IV). There was also a significant association between the use of antimicrobials for acute otitis media and cumulative prevalence of tympanostomy tube placement as observed on the community level when plotting the data for the different areas studied 2003 (IV). In Figure 18, changes in the use of tympanostomy tubes over the last five years are plotted against changes in use of antimicrobials (as a percentage) for acute otitis media in the different areas involved. Even though the association was not statistically significant (p = 0.138), in area E, there was a concomitant and significant decrease both for tympanostomy tube placements in children and for antimicrobial treatment of acute otitis media as mentioned earlier (IV).

Effects of tympanostomy tubes on recent antimicrobial drug consumption In 2003, of a total of 123 children having tubes (at present), 49 (40%) had received oral antimicrobials at least once during the previous 8 weeks, compared with 124 of 737 children (17%) without tubes (p<0.001). Considering only antimicrobial treatment for acute otitis media, 25 children (20%) in the tympanostomy group had recently received antimicrobials, compared with 74 children (10%) among those without tubes (p<0.001). Adjusting for age, the odds ratio for receiving antimicrobials recently was significantly higher for children with tubes (p<0.001) (IV). In 1998, this difference was not statistically significant (III).

Antimicrobial resistance in pneumococci (I, II, V) Carriage of penicillin-nonsusceptible pneumococci In the 1993 study, including only children 1-6 years old, pneumococci were found in 426 (53.9%) of 791 children. In 36 (8.5% of all children carrying pneumococci), the pneumococci were penicillin- nonsusceptible. In the 1998 study, pneumococci were found in 384 39

Differences in cumulative prevalence (%) of tympanostomy tube placements in children between 1998 and 2003 38 34 r = 0.862 30 p = 0.138 26 22 18 14 Area H 10 Area V 6 2 -2 Area E -6 Area B -10 -14 -18 -22 -26 -30 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 Changes (%) in the number of antimicrobial treatments per child per year for otitis media between 1998 and 2003

Fig. 18. Differences in the use of tympanostomy tubes (cumulative prevalence) in relation to change (%) in the use of antimicrobials (yearly incidence) for acute otitis media between 1998 and 2003 for the different studies areas.

(51.7%) of 743 children, and in 31 (8.1% of all children carrying pneumococci), the pneumococci were penicillin-nonsusceptible. In the 2003 study, 525 of 824 children studied (63.7%) carried pneumococci, and 50 (9.5%) were penicillin-nonsusceptible. If only typeable strains of pneumococci are taken into account, then 31 (5.9%) were penicillin-nonsusceptible in the 2003 study. A comparison between the three study periods concerning prevalence of PNSP is shown in Table 7. The carrying rate was highest in area V in the 1993 study (18.2%), in area E in the 1998 study (18.8%) and in area H in the 2003 study (13.0% or 10.6% if nontypeable strains are excluded) (II, V). 40

Table 7. Prevalence of penicillin-nonsusceptible pneumococci as observed in the studies in 1993, 1998 and 2003. Study year Total study Pneumococci Penicillin-nonsusceptible group present pneumococci present Number Number Number %1 1993 791 426 36 8.5 1998 743 384 31 8.1 2003 824 525 50 9.5 2003 824 525 31a) 5.9 2003 824 525 19b) 3.6 1Of all pneumococcal carriers, a) Typeable-stains, 2003 b) Non-typeable (non-encapsulated) strains, 2003

Table 8 shows the numbers of children carrying pneumococci and percentages carrying PNSP in the 1993 study. Resistance was more common in the youngest children, those less than two years of age, compared with the children who were 2-6 years of age (I). This association was confirmed by multivariate analysis. In the 1998 study, age was also significantly associated with the presence of PNSP in univariate analysis (II), while no significant association was observed in the 2003 study (V).

Table 8. Penicillin-resistant pattern for pneumococci in children in the 1993 study by age groups. Study year Total study Pneumococci Penicillin-nonsusceptible group present pneumococci present Number Number Number %1 <2 years 238 114 23 20.2 2-6 years 681 370 24 8.1 1Of all pneumococcal carriers,

Carriage of erythromycin-resistant pneumococci Antimicrobial susceptible testing was done for all pneumococcal colonies, both penicillin-susceptible and penicillin-nonsusceptible. As shown in Table 9, resistance to trimethoprim-sulfamethoxazole is not so uncommon among penicillin-susceptible pneumococci and erythromycin resistance among penicillin-susceptible pneumococci 41 increases significantly between 1998 (II) and 2003 (from 2% to 7.8%, p < 0.001) (V). They increased in areas H and V (p = 0.0004 and p < 0.0001, respectively), but decreased in the other two areas (E and B, p = 0.05 and p = 0.6, respectively). However, the proportion of erythromycin-resistance among PNSP decreased in 2003 but though not significantly (p<0.1), mainly because of increased rate of erythromycin-susceptible PNSP, serotype 9V (in area H) and 14 (in area E) (V).

Penicillin-resistance among pneumococci and antimicrobial use When analysed for all areas combined, the prevalence of carrying PNSP remained similar during the years studied, but decreased for serotype 6B (Fig. 19), at the same time as antimicrobial use dimin-

%PNSP (typeable and nontypeable strains) %PNSP (typeable strains only) %PNSP serotype 6B Antimicrobial sales Antimicrobial use in the sampled groups 1.8 14 1.6

12 1.4

10 1.2

1.0

%PNSP 8 0.8 6

0.6 courses/child/year

4 Number of antimicrobial 0.4

2 0.2

0 0.0 1993 1998 2003

Fig. 19. Changes in antimicrobial use among 1-6 year old children in the four study areas and the carriage rate of penicillin-nonsusceptible pneumococci (PNSP) 1993, 1998 and 2003. Data from antimicrobial sales statistics in study areas for children < 7 years old, 1992-1993 and 1997-1998, are also shown for comparison. 42

Table 9. Number (No) of penicillin-susceptible (PSP) and nonsusceptible pneumococci (PNSP), which are nonsusceptible (intermediate or resistant) to erythromycin (ERY), tetracycline (TET) chloramphenicol (CHL) and trimethoprim- sulfamethoxazole (SXT) according to disc diffusion tests, in 1993, 1998 and 2003, in respective study areas. Area Year ERY TET CHL SXT No No % No % No % No % H PSP 1993 256 0 0 1 3.0 0 0 62 24.4 1998 163 1 0.6 1 0.6 0 0 46 28.8 2003 134 13 9.7 2 1.5 0 0 34 25.4 PNSP 1993 24 20 83.3 22 91.7 13 54.2 24 100 1998 11 7 63.6 8 72.7 8 72.7 11 100 2003 20 10 50.0 10 50.0 4 20.0 20 100 V PSP 1993 45 2 4.4 2 4.4 0 0 17 37.8 1998 117 0 0 0 0 0 0 25 20.7 2003 199 21 10.6 3 1.5 0 0 50 25.1 PNSP 1993 10 9 90.0 9 90.0 10 100 10 100 1998 5 5 100 5 100 5 100 5 100 2003 15 14 93.3 14 93.3 9 60.0 15 100 E PSP 1993 51 0 0 0 0 0 0 12 23.5 1998 56 4 7.1 2 3.6 0 0 10 17.9 2003 108 1 0.9 0 0 0 0 41 38.0 PNSP 1993 1 1 100 1 100 1 100 1 100 1998 13 13 100 13 100 13 100 13 100 2003 12 8 66.7 7 58.3 0 0 12 100 B PSP 1993 38 0 0 0 0 0 0 6 15.8 1998 17 2 11.8 2 11.8 0 0 12 70.6 2003 34 2 5.9 0 0 0 0 2 5.9 PNSP 1993 1 1 100 1 100 1 100 1 100 1998 2 2 100 2 100 1 50.0 2 100 2003 3 2 66.7 2 66.7 0 0 3 100 TOTAL PSP 1993 390 2 0.5 3 0.8 0 0 97 25.0 1998 353 7 2.0 5 1.4 0 0 93 26.6 2003 475 37 7.8 5 1.1 0 0 127 26.7 PNSP 1993 36 31 86.1 33 91.6 25 69.4 36 100 1998 31 27 87.1 28 90.3 27 87.1 31 100 2003 50 34 68.0 33 66.0 13 26.0 50 100 43 ished by about one third from 1993 to 2003. The association between changes in antimicrobial use and the carrying rate of PNSP, multiresistant, serotype 6B (Spain6B-2) over the 10 years in each area will be described below (Fig. 24).

Associations with PNSP-carrying in children carrying pneumococci Already at the time of the first study in 1993 (Paper I), the prevalence of PNSP was higher among children who had taken antimicrobials. Of 317 children participating in the 1993 study who had received antimicrobials during the preceding year, 44 (13.9%) carried PNSP compared with 3 out of 167 (1.8%) of those who had not received antimicrobials during the preceding year (p<0.001). Antimicrobial use was also found to be significantly associated with the carriage of PNSP in the 1998 and 2003 studies (II, V). This was confirmed with multivariate analysis of the data (I, II, V) as an increasing risk of PNSP carriage with an increasing number of antimicrobial treatment courses. When the data were examined specifically for treatment of acute otitis media in the 1998 (II) and 2003 studies (data not shown), this association also held true (p<0.001). Table 10 shows the results of a multivariate, backward, stepwise, logistic model including the factors discussed above, together with some other factors that had proved statistically significant in relation to antimicrobial resistance in univariate statistical analyses (II, V). Data from 1993 were recalculated to make them comparable. Excluding the number of antimicrobial treatments that were significantly associated with PNSP carriage in all three analyses, age and residence were inconsistently found to be independent risk factors for carriage of PNSP. No single antimicrobial class could conclusively be shown to be more definitively associated with carriage of PNSP in all the three studies. However, some treatment groups were small. In the 1993 study, trimethoprim-sulfamethoxazole was significantly associated with carriage of PNSP by univariate analysis (I). Children in area V had significantly higher odds than other children of carrying PNSP in 1993 by multivariate analysis (I), and the PNSP, multiresistant, serotype 6B prevalence has remained surprisingly stable in this community between 1998 and 2003 (V). The most likely explanation was 44

Table 10. Odds ratio (OR) of carrying penicillin-nonsusceptible pneumococci as opposed to penicillin-susceptible pneumococci by backward, stepwise, logistic regression method in the studies in 1993a), 1998b) and 2003c). Variable Number OR 95% CI P value Age, 1993a) 424 0.70 0.52-0.96 0.025 Residence, 1993a) Area H 279 1 (reference area) Area V 55 2.62 1.00-6.81 0.048 Area E 52 0.23 0.03-1.81 0.163 Area B 38 0.31 0.04-2.43 0.266 Number of antimicrobial treatments in last 12 months, 1993a) 424 1.32 1.11-1.58 0.002 Residence, 1998b) Area H 170 1 (reference area) Area V 122 0.519 0.17-1.62 0.260 Area E 67 4.139 1.65-10.39 0.003 Area B 19 1.852 0.36-9.50 0.460 Number of antimicrobial treatments in last 12 months, 1998b) 378 1.50 1.23-1.82 0.0001 Number of antimicrobial treatments in last 12 months, 2003c) 506 1.28 1.11-1.48 0.007 a) Number of children in analysis, 1993 = 424, X2 = 35.87, df = 5, p < 0.0001. b) Number of children in analysis, 1998= 378, X2 = 25.49, df = 4, p < 0.0001 (II). c) Number of children in analysis, 2003= 506, X2 = 10.412, df = 1, p = 0.013 (V). much higher total use of antimicrobials, especially trimethoprim-sulfamethoxazole and erythromycin in 1993 (I) and azithromycin in 2003 (V) in this area. The carriage rate of PNSP was also associated with the lapsed time since the last course of antimicrobials as shown in Figure 20. As seen in the figure, the prevalence of PNSP was higher in children who had taken antimicrobials recently (last 2-7 weeks). The observation of an association between recent antimicrobial use and carriage of PNSP was confirmed in multivariate analysis of data from all phases of our studies. Recent antimicrobial use (2-7 weeks since last treatment) instead of the number of antimicrobial courses 45

% 30

20 p<0.001 p=0.002 p<0.001 2-7 weeks 15 8-52 weeks 23/81 11/51 16/60 no treat- 10 ment p<0.101

5 p<0.026 15/206 8/142 18/182

3/155 12/191 16/283 0 1993 1998 2003

Fig. 20. Carriage rate of penicillin-nonsusceptible pneumococci (PNSP) of all children carrying pneumococci, 1-6 years of age, related to time from last antimicrobial treatment (2-7 weeks or 8-52 weeks) or no treatment in the studies in 1993, 1998, and 2003. in the preceding 12 months was the only variable constantly associated with PNSP carriage in all the analyses from the three studies (V). Figure 21 shows the odds ratio for different variables studied in 1993, 1998 and 2003 by using the results of similar multivariate logistic models, including all possible risk factors for PNSP carriage against carriage of penicillin-susceptible pneumococci. The passage of 2-7 weeks from the last antimicrobial treatment compared with > 8 weeks, was consistently the only significant risk factor for carriage of PNSP in all three analyses.

Risk of PNSP carriage after receiving antimicrobials for all children (i.e., not only those carrying pneumococci) In our first study in 1993 (I), 580 children of 919 had received antimicrobials over the previous 12 months, and 191 had received treatment 2-7 weeks before sampling, of which 27 were carrying PNSP, as opposed to only 17 out of 389 children who had received antimi- 46

Odds ratio 7 6 5 4 3 2 1 0 Boys 1993 Boys 2003 Boys Boys 1998 Boys Day care 1993 care Day 1998 care Day 2003 care Day Hf./Vestm.1998 Hf./Vestm.1993 Hf./Vestm.2003 Age in years 2003 in years Age Age in years 1998 in years Age Age in years 1993 in years Age Bol.vik/Vestm.1993 Bol.vik/Vestm.2003 Bol.vik/Vestm.1998 Egilsst./Vestm.1993 Egilsst./Vestm.2003 Egilsst./Vestm.1998 Number siblings 2003 Number siblings 1993 Number siblings 1998 Smoking 2003 in the household, 2-7 weeks from last AM treatm. 2003 treatm. last AM from 2-7 weeks 2-7 weeks from last AM treatm. 1993 treatm. last AM from 2-7 weeks 2-7 weeks from last AM treatm. 1998 treatm. last AM from 2-7 weeks History 2003 tubes, of tympanostomy History 1998 tubes, of tympanostomy Fig. 21. Adjusted odds ratio (95% confidence interval) for carrying penicillin-nonsusceptible pneumococci (PNSP) or not according to multivariate logistic regression analysis in studies in 1993, 1998 and 2003. (Number of children in analysis 1993 = 426, X2 = 46.72, df = 8, p < 0.0001. Number of children in analysis 1998 = 384, X2 = 22.12, df = 9, p = 0.0085. Number of children in analysis 2003 = 510, X2 = 31.47, df = 11, p = 0.0009)

crobials 8-52 weeks before study entry (p<0.0001). Corresponding figures from the 1998 study (II) show that of 743 children, 372 had received antimicrobials in the previous 12 months; thereof 11 of 129 children receiving antimicrobials in the previous 2-7 weeks carried PNSP, as opposed to only 8 out of 243 children receiving antimicrobials 8-52 weeks before sampling carrying PNSP (p=0.045). Cor- responding figures for the 2003 study (V) show that of 824 children, 357 children had received antimicrobials in the preceding 12 months. Of these 16 out of the 104 children that had received antimicrobials 47

Carrying ratio 0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

PSP 2-3 weeks PSP 4-5 weeks PSP 6-7 weeks PSP 8-9 weeks PNSP 2-3 weeksPNSP 4-5 weeksPNSP 6-7 weeksPNSP 8-9 weeks PSP 10-11 weeksPSP 12-13 weeksPSP 14-15 weeksPSP 16-17 weeksPSP 18-19 weeksPSP 20-21 weeksPSP 22-23 weeksPSP 24-25 weeks PNSP 10-11 weeksPNSP 12-13 weeksPNSP 14-15 weeksPNSP 16-17 weeksPNSP 18-19 weeksPNSP 20-21 weeksPNSP 22-23 weeksPNSP 24-25 weeks

PSP 26 weeks or more PNSP 26 weeks or more

Fig. 22. Carriage rate (95% confidence interval) of penicillin-susceptible (PSP) (green) (n=648) and penicillin-nonsusceptible pneumococci (PNSP) (red) (n=97) by all children receiving antimicrobials during the 12 months prior to study entry (n=1315) for the 1993, 1998 and 2003 studies, by the number of weeks from the last antimicrobial treatment. in the preceding 2-7 weeks carried PNSP, as opposed to only 18 out of 253 children receiving antimicrobial treatment 8-52 weeks before sampling carrying PNSP (p=0.027). Figure 22 shows the carriage of penicillin-susceptible (PSP) and PNSP of all children receiving antimicrobials (i.e., not only of those carrying pneumococci) for the three studies by the number of weeks from the last antimicrobial treatment. Relatively speaking the number of PSP strains are similar to the number of PNSP strains two to three weeks after antimicrobial treatment. 48

% PNSP 8 6B 19F 7 23F 9V 6 14 Non-typeable

0 1993 1998 2003

Fig. 23. Spread of different serotypes of penicillin-nonsusceptible pneumococcus (PNSP) as carrying ratio (%) of all pneumococci observed in the studies in 1993, 1998 and 2003.

Factors associated with carriage of erythromycin-resistant pneumococci All the variables tested for association with carriage of PNSP were also tested for association with carriage of erythromycin-resistant pneumococci with a multivariate, backward, stepwise, logistic regression model in the 2003 study (V). As for PNSP carriage, the number of antimicrobial treatments was the only independent risk factor for carriage of erythromycin-resistant pneumococci, with an odds ratio of 1.18 for each treatment (95% CI 1.03-1.35), p=0.0157.

Spread of resistant strains In the 1998 study the carrying rate of PNSP, multiresistant, serotype 6B, 7.5%, was similar to the 1993 study, 7.7% but decreased in the 2003 study to 2.5% (p <0.001). On the other hand, new typeable PNSP strains (seroptypes 9V and 14) appeared in 2003 along with a new non-typeable (non-encapsulated) serotype, as shown in Fig. 23 49

Egilsstadir Vestmannaeyjar 25 3.0 25 3.0

20 2.5 20 2.5 2.0 2.0 15 15 1.5 1.5 10 10 1.0 1.0 % PNSP type 6B % PNSP type 6B courses/child/year courses/child/year 5 5 0.5 0.5 Number of antimicrobial Number of antimicrobial 0 0.0 0 0.0 1993 1998 2003 1993 1998 2003

Bolungarvik Hafnarfjordur 25 3.0 25 3.0

20 2.5 20 2.5 2.0 2.0 15 15 1.5 1.5 10 10 1.0 1.0 % PNSP type 6B % PNSP type 6B courses/child/year 5 0.5 courses/child/year 5 0.5 Number of antimicrobial Number of antimicrobial 0 0.0 0 0.0 1993 1998 2003 1993 1998 2003

Fig. 24. The prevalence of penicillin-nonsusceptible pneumococci (PNSP) of multiresistant serotype 6B (the Spain6B-2 clone) as a carriage rate of all pneumococci and use of antimicrobials in the sample groups, as observed in the study areas in the 1993, 1998 and 2003 studies (♦---♦). Data from antimicrobial sales statistics in the study areas for children < 7 years old, 1993 and 1998 are also shown for comparison (•---•).

(V). The new non-typeable PNSP serotype was found in all study areas. Serotype 9V was found only in area H and a new serotype 14 only in area E.

Clonal spread of PNSP of multiresistant 6B strain (Spain6B-2) in different communities When studying different areas separately, obvious differences between how the prevalence of PNSP of multiresistant serotype 6B (phenotypically identical according to antibiotic susceptibility test- 50 ing as the Spain6B-2 clone) changed in these areas were observed (II, V). The PNSP 6B strain was quite common in area V and area H in the south, near Reykjavik, the capital of Iceland, already in the 1993 study but decreased in the next two studies (Fig. 24). This may be compared with what was observed in areas E and B in the east and west, remote areas, where the prevalence was low in the 1993 study but increased considerably in 1998 and had disappeared again in 2003. As can also be seen in Figure 24, the use of antimicrobials was lower in the later studies, but there seems to be no obvious correlation between total use of antimicrobials in the community for children and increase or decrease in the prevalence of the multiresistant PNSP 6B strain (the Spain6B-2 clone). 51 DISCUSSION

Starting-points when planning the studies There were many reasons for focusing my research in primary healthcare in Iceland on upper respiratory tract infections and the use of antimicrobials drugs among children. Upper respiratory tract infection and especially acute otitis media, continues to be one of the most common childhood infections and source of morbidity in children (Söderström 1995; Rovers et al. 2004). Acute otitis media is one of the commonest reason for a child visiting a GP, and also the most common reason for antimicrobial prescription (McCaig and Hughes 1995; Arason et al. 1996; McCaig et al. 2002; Rovers et al. 2004). The prevalence of PNSP of multiresistant serotype 6B (now recognised as Spain6B-2) increased rapidly in Iceland after its first appearance 1989. The prevailing knowledge at that time indicated a causal relationship between antimicrobial use and development of resistant strains of pathogens not only in hospital settings (McGowan 1983) but also possibly in communities (Molstad et al. 1988; Molstad and Hovelius 1989; Eliasson et al. 1990; Molstad et al. 1992; Reichler et al. 1992). GPs’ prescription pattern in different areas have been shown to differ, which might make a study of antimicrobial prescription in relation to bacterial resistance pattern both interesting and important. When planning the study, it was known that the prescription of antimicrobials was commoner in Iceland than in the other Nordic countries. Acute otitis media in a child was found to be the most common reason for prescribing an antimicrobial for a child, and this was a reason for focusing the study on children with special reference to the treatment of acute otitis media. International rates of antimicrobial prescriptions and tympanostomy tube placements for otitis media vary greatly, which can be explained largely by the lack of uniform evidence-based guidelines (Schilder et al. 2004). Al- though tympanostomy tube placement has been a well-established treatment option for chronic effusion in the middle-ear and recurrent episodes of acute otitis media, the prevalence rate of tympanostomy tube placements in Iceland during the planning of phase II of this 52 study was not known at that time. It was therefore deemed of interest to include a study of tympanostomy tubes in the study plan, with special focus on the potential association between frequent use of antimicrobials and the tympanostomy tube placement rate on the community level, especially in the third phase of the study where time trends could also be observed. Iceland should be a suitable country for studying the associations between antimicrobial use and the development of resistance in common pathogens like pneumococcus in the community. Prescrip- tion patterns can easily be described, thanks to: computerised information in the primary healthcare centres, computerised information from the local pharmacies and the organisation of healthcare in Ice- land, where people, at least outside the capital of Reykjavik, visit their own primary healthcare centre and their own pharmacy. Be- cause of the special geography of Iceland, areas are, to some extent, isolated from each other; this makes it easier to study changes in resistance patterns or to follow up newly recognised resistant clones. Furthermore, the prescription patterns of GPs in different areas has been shown to differ in Iceland, which might make a study of antimicrobial prescription in relation to bacterial resistance patterns even more interesting.

Performance of the studies This thesis is mainly based on the following basic examinations: • Prescription studies on all antimicrobial sales, carried out in 1992-1993 and 1997-1998, including all ages, and involving the pharmacies of the study areas. • Sampling of nasopharyngeal bacteria, cultivation for pneumococci with serotyping of PNSP strains and study of their resistance pattern; this sampling included children up to 6 years old in 1993 and was confined to children 1-6 years old in 1998 and 2003. • Questionnaire about socio-demographic factors and history of previous use of antimicrobials and causes in the same children and on the same occasions as mentioned in the preceding point. • Questionnaire to parents about personal preferences in relation 53 to antimicrobial treatment for upper respiratory tract infections 1998 and 2003. • Questionnaire about previous and present history of tympanostomy tube use in 1998 and 2003.

It was possible to carry out all these examinations according to plan. The co-operation with the local pharmacies was excellent, as was the co-operation with the GPs and other personnel at the involved primary healthcare centres and the laboratory where pneumococci cultivation was done. The co-operation with the personnel at the day care centres as well as with the children and their parents was also very good, and in the studies based on random sampling or all available children (II-V), the participation rates were high, 75-90%. In the first phase, where sampling was from all available sick and healthy 0-6-year-old children, the participation rate was also high (15-38% of total population under 7 years old). In summary this means that the prerequisites and the performance of the different examinations were of high quality, facilitating the drawing of safe (accountable) conclusions when analysing the data.

Antimicrobial use The use of drugs by sales statistics, measured as number of defined daily doses (DDD) per 1000 inhabitants per day, is useful when comparing nations and whole communities (Medicines consumption in the Nordic countries http://www.nom-nos.dk/nomesco.htm , last viewed Mai 2006 ; Goossens et al. 2005). One defined daily dose is by defini- tion the certain therapeutic amount (for example in milligrams) of a drug needed by an adult person per day. Although this calculation can be used to describe the amount (in milligrams) used in each age group, it does not give a clear picture when comparing therapeutic doses for children and adults. Therefore, the prescription rate (incidence rate) is better for demonstrating differences in consumption between children and adults as was demonstrated in Figure 7. As observed in a previous Icelandic study (Njalsson and McAu- ley 1992), women use the healthcare centres more than men and use more drugs. This is also true regarding the use of antimicrobials 54 specifically, as shown in our study. It is, however, worth noting that this gender difference first becomes apparent in the early teenage years. This is in accordance with results from other studies showing that women have more episodes of respiratory tract infections than men, probably due to the fact that women have closer contact with children, both at home and in child-related work (Monto and Ullman 1974; Söderström 1995). Seasonal variation with the highest peak of antimicrobial use in late winter has been reported from previous studies (Söderström 1995; Goossens et al. 2005). It was also confirmed in our study. Viral infections like the common cold are far more common than bacterial infections (Benediktsdottir 1993; Monto 1994; Söderström 1995) and more common during the winter, but it can sometimes be hard to distinguish accurately between viral and bacterial infections clinically (Heikkinen and Chonmaitree 2003). This can partly explain why antimicrobial prescriptions are so prevalent during the winter in Iceland like in other countries with heightened winter peaks with high yearly use of antibiotics (Goossens et al. 2005). This means also that the peak load of infections in people seeking healthcare service in Iceland is during late winter, and this was one of the reasons that we mainly collected the nasopharyngeal specimens March to May. A child with a bacterial upper respiratory tract infection often has a clinical picture of symptoms involving more than one site, including the middle-ear, nose and throat. The higher prescription of antimicrobials for sinusitis in 1998 and 2003 than in 1993 possibly depends on a shift from stating acute otitis media as the main diagnosis to sinusitis when prescribing antimicrobials is deemed to be needed. In others studies, antibiotics are also frequently prescribed for children with unspecified upper respiratory tract infections and bronchitis, despite recommendations to the contrary (Howie 1983; Hamm et al. 1996; Schwartz et al. 1997; Nyquist et al. 1998; Wang et al. 1999). A frequent claim, which has not been adequately studied, is that restrictions in social security systems make people go to work even though they or their children suffer from infections. As a con- sequence of this social pressure, children “have to” be treated with anti-infective drugs to be able to go to school or day care centres (Agenas et al. 1995; Jonsson and Haraldsson 2002). 55 A phenomenological investigation in Iceland of why GPs prescribe antimicrobials in cases when there are no clear signs of bacterial infections, called “non-pharmacological prescriptions of antibiotics” concludes that the principal causes of such use of antibiotics are “the lack of stable doctor-patient relationships due to lack of continuity in medical care, pressure from patients in a stressful society, physician’s work pressure, the physician’s own personality, particularly the earnings incentive and service mentality and, last but not least, the physician’s lack of confidence and uncertainty, resulting in use of antibiotic prescriptions as a coping strategy in an uncomfort- able situation” (Petursson 2005 a). Antibiotic utilisation among Icelandic children, age < 7 years, in our study 1998 (II), varied between areas in similar amount (from 7.6 to 17.1 DDD/1000 children/day) as was shown in others studies the same year between various Danish and Swedish counties (from 8.0 to 19.7 DDD/1000 children/day) (Melander et al 2000; Melander et al. 2003). “The observed variations in antibiotic prescribing may reflect different parental and/or prescribes attitudes towards use of antibiotics and they emphasise that antibiotic prescribing is influenced by factors other than the prevalence of bacterial infections. Relationships between socio-economic position (educational level) and drug utilisation should not be generalised from one area to another” (Melander et al. 2003). The first part of the study was followed by an unstructured nationwide campaign to reduce unnecessary antimicrobial use for upper respiratory tract infections, mainly in children. The interventions consisted of information and education of both the public through mass media and of physicians through meetings and the Icelandic Medical Journal. Prudent antimicrobial use was encouraged especially for acute otitis media. New antimicrobial prescription guidelines were prepared and made available on the Internet (1997) http:// lyf.landlaeknir.is/Brad_eyrnabolga_barna.htm (last viewed in Janu- ary 2006). Simultaneously a greater reduction in antimicrobial sales for trimethoprim-sulfamethexazole statistics was observed than for other antimicrobials. Indirect effect of social (parental educational level) and climatological factors (on infection rate) on antimicrobial use are possible but unlikely in our study but are reported to be indi- 56 rect force on antimicrobial use and resistance in Spain (Garcia-Rey et al. 2004). A national ambulatory medical survey in North-America show dramatic decline (~40%) in the population based prescribing of antimicrobial agent to children and adolescents from 1990 to 2000 and 47% decline because of otitis media specifically (McCaig et al. 2002). The bad news is that during the 1990´s, a shift occurred from using targeted narrow-spectrum antimicrobials (the second compo- nent of appropriate antimicrobial use) to broad-spectrum antimicrobials for children, from 23% to 40% (Steinman et al. 2003). The use of second-generation macrolides (including azithromyzin) among children has increased dramatically in North-America, even among younger children, for whom use for initial treatment of illness is not recommended (Stille et al. 2004). Changes in antimicrobial prescribing in our study and increasing use of broad-spectrum antimicrobials in some study areas along with high antimicrobial use will however be further discussed her below in connection with changes in the antimicrobial treatment options for acute otitis media over the study period and in the chapter “Amount and type of antimicrobials associated with resistance in the community”. The incidence of antimicrobial treatments because of acute otitis media was found to be similar in our 2003 study as has been reported to the incidence of diagnosed acute otitis media for children in earlier studies from the United States (Teele et al. 1989; Paradise et al. 1997) and from Finland (Alho et al. 1991). There is more opportunity for the spread of respiratory infections and also a higher rate of acute otitis media among children in day care settings (Wald et al. 1988; Uhari et al. 1996; Rovers et al. 1999). In our studies, ~80% of all the children attended day care. The child’s age (younger age), residence in a high antimicrobial consumption area and history of tympanostomy tubes (past or present), were independently associated with the number of antimicrobial treatments for acute otitis media (IV). In the 1998 study (III), this was only the case for younger age and the high antimicrobial consumption area. The prescription of antimicrobials for children, particularly the prescriptions for acute otitis media, decreased considerably in the communities over the study period; in some areas the decrease is dramatic. The difference in prescriptions of antimicrobials was rath- 57 er small between different areas at the beginning of our study period, but increased, and, at the end of the period, it was three times higher in the area where the prescription rate was highest, compared with the area where it was lowest. Not only is the prescription rate of antimicrobials different from one area to another in the end of our study but also the choice of an antimicrobial agent when prescribing an antimicrobial. Broad-spectrum antimicrobials, especially azithromycin, were more often prescribed in areas where the total antimicrobial use was highest. Success in this aspect in some areas and not others is of special interest and may have complex explanations. A recent study addressed the phenomenon of varying clinical “mindlines” among primary healthcare practices in the United King- dom (Gabbay and le May 2004). The authors found out that expe- rienced GPs rarely use explicit evidence from research. They create shortcuts in their decision making, based on a combination of inputs and impulses from their professional surroundings, such as trusted colleagues and opinion leaders, written guidelines, material from patients, and pharmaceutical representatives. Parents in the area where antimicrobial consumption was lowest and narrow-spectrum antimicrobials were most often used, were less likely to be in favour of antimicrobial treatment (III, IV). The response from parents to the questionnaire addressing issues of parental expectations and awareness, further indicated that parents who consider it inappropriate to treat unspecified upper respiratory tract infections with antimicrobials significantly more often preferred that acute otitis media not be treated with antibiotics (III). These variations in parental attitude together with a significant correlation at the community level between the children’s total use of antimicrobials and the percentage of parents considering it sometimes appropriate to treat a common cold with antimicrobials (IV), may be important observations in this study as primary care physicians maintain that parental pressure and expectations in relation to antimicrobial drug prescriptions represent an important barrier to restrictive prescription practices (Macfarlane et al. 2002; Garbutt et al. 2003; Siegel et al. 2003; Petursson 2005 b). The high percentage of parents considering it sometimes appropriate to treat a common cold with antimicrobials in our studies is in accordance with results from study conducted in 58 the United States where misconception about the appropriate treatment for colds was concluded to be predictive of increased health service utilization (Lee et al. 2003). Other studies have shown a tendency to reduce antimicrobial treatments for acute otitis media in children in tandem with parents’ acceptance of the reduction, through educational intervention with parents, watchful waiting and safety-net antibiotic prescription (Little et al. 2001; Smabrekke et al. 2002; Siegel et al. 2003; McCormick et al. 2005). It seemed that the prescribing doctor’s habits were adopted by the parents when dealing with children with upper respiratory tract infections in our studies (III, IV). It is reasonable to believe that parents’ views reflect the information given in mass media and during discussions with the healthcare personnel (nurses as well as GPs). This is in accordance with the observation that healthcare practices can function like “families”, where habits or indirect rules are created (Gabbay and le May 2004). Variations in parental attitude toward antimicrobial treatment may therefore be important and are possibly part of the above-mentioned “mindlines”. Possible causative explanation of success in diminishing antimicrobial use in some areas but not others may be explained by possible correlation between non-antimicrobial drug use for acute otitis media specifically and lower risk of relapsing episodes of acute otitis media later and therefore decreasing need for antimicrobials as will be discussed below in the next chapters in connection with changes in the microflora of the nasopharynx after antimicrobials use.

Tympanostomy tube placements Our feeling that tympanostomy tubes were common was confirmed in our studies, and we also found that it was more common than in other countries (Paradise et al. 1997; Coyte et al. 2001; Desai et al. 2002; Schilder and Rovers 2003). In a recent Finnish otitis media vaccine trial study, children were followed up to 24 months of age (Palmu et al. 2004). Tympanostomy tube placement and/or adenoidectomy were performed in 24.1% and 20.6% of the children in the control and trial group, respectively (not significant difference). Tympanostomy tube placement, though, was much less common in the south of Sweden, where ~10% of children had a history of tym- 59 panostomy tube insertion (Melander et al. 1998). This contrasts also somewhat to results from the United States, where the incidence of acute otitis media among children seems to be similar to that in Ice- land but the rate of tympanostomy tube placements is generally much lower (<5%) and may therefore need further explanation (Teele et al. 1989; Paradise et al. 1997; Thompson et al. 1999). However, rates of ~30% for surgery are reported in the United States in some areas (Myer and France 1997). Other studies have shown substantial area variation or an almost 10-fold difference between the areas with the highest and lowest rates (Coyte et al. 2001). Small-area variation in surgical rates of tympanostomy tube placements in United States has raised concerns about access to care, appropriateness of treatment, and the quality and cost of care (Coyte et al. 2001). In our studies, variation in the tympanostomy rate between areas was not so big in the beginning of our studies, but more interestingly, the rate changed over-time even though there were not so many changes in GP positions in the areas, and the same otolaryngologists served in the areas over the entire study-period. Therefore an explanation other than small-area variation is more likely to explain our results, like other non-causative explanation like intervention in the recommended indication for tympanaostomy tube placements and/or causative explanation like changes in the rate of chronic or recurrent otitis media in the areas or both as was mentioned above and will be discussed further in the chapter “Associations between acute otitis media, antimicrobial use and tympanostomy tube placements” below.

Antimicrobial use and carriage of antimicrobial-resistant pneumococcus As mentioned in the introduction, the first case of PNSP in Iceland was observed in 1988 (Kristinsson et al. 1992) and in the following years most of them proved to be a multiresistant serotype 6B strain, probably coming from Spain, where this clone, now registered as Spain6B-2, had previously been observed (Soares et al. 1993). Later on it was shown that the prevalence of this strain increased rapidly. When our study started, the cultivation of bacterial sampling from hospital series (patients) indicated a PNSP prevalence rate of about 20%, almost all of them (~80%) being multiresistant serotype 6B 60 (Kristinsson 1995). The prevalence in the community was not known at that time. Comparative and analytical studies have demonstrated a relationship between high antibiotic consumption and increasing penicillin-resistance among pneumococci. In few reported epidemiological studies for whole communities like in our studies (I, II, V) and some others (Melander et al. 1998), this correlation was found not only for antimicrobial use by whole communities (comparative and indirect relationship) like in some others studies (Melander et al. 2000; Granizo et al. 2000; Dias and Caniça 2004; García-Rey et al. 2004; Goossens et al. 2005) but also for individual antimicrobial use (analytical and causative relationship). It is therefore of interest to observe the big differences in the prevalence of antimicrobial resistance among pneumococci from time to time in the separate areas with interplay of other possible risk factors for individual carrying in our studies, especially because the increase in the prevalence of PNSP 1993 and 1998 was almost solely due to an increase in one particular strain, multiresistant serotype 6B which was shown to be phenotypically identical by antibiotic susceptibility testing as the Spain6B-2 clone and may be explained by a novel clonal spread into “virgin” communities and possible herd immunity could therefore be better defined as will be discussed later in the chapter “Clonal spread in the community”. Studies of the individual relationship between antimicrobial use and resistance in pneumococci have produced conflicting results, reflecting differences in the study design, setting, and measures of association used (Lipsitch 2001). In previously published studies the carriage rate of resistant pneumococci has usually been calculated with the total number of children carrying pneumococci as the de- nominator. In all our three cross-sectional studies, the risk of carrying PNSP was 4-5 times greater during the first 7 weeks after each antimicrobial course for children actually carrying pneumococci. Antimicrobial treatment does though not appear to increase an individual’s absolute risk of carrying PNSP after treatment in some studies. However, it may increases a patient’s relative risk of carriage of PNSP (Lipsitch 2001). In French prospective studies, antimicrobial treatment did not increase the risk of an individual child carrying PNSP even though the proportion of PNSP increased (i.e., only for 61 those carrying pneumococci) (Cohen et al. 1997; Varon et al. 2000). This was mainly explained by a significant decrease in the number of individuals carrying penicillin-susceptible pneumococci after having received antimicrobials and thereby relatively higher PNSP rate (relative risk) among those still carrying pneumococci. Because of the above-mentioned observations, we recalculated the data from all three studies for all children, i.e., not only those carrying pneumococci. The results were nevertheless identical to those that had been obtained before i.e., higher (absolute) risk of PNSP carriage for all children recently after antimicrobial treatment. Our results are therefore not congruent with the results from the French prospective studies. We conclude that current antimicrobial use en- courages the uptake of resistant pneumococci and subsequent colonisation or “selective acquisition of (foreign) nonsusceptible strains” from the outer ecosystem (from the community). In addition, PNSP not previously detected by our methods may proliferate and become abundant and detectable after antimicrobial treatment (unmasking of dormant and/or nonsusceptible strains present in very low numbers from the mucosa). This may be supported by the fact that in our last study, carriage of 2-3 strains was not uncommon (sometimes both penicillin-susceptible and nonsusceptible) (V). Detection of multiple pneumococcal carriages by our culture methods is though not possible unless the strains exhibit different colonial morphologies. In vitro studies show that low doses of beta-lactam antimicrobials can increase the growth of both intermediate and resistant pneumococci in cultures on agar plates (Negri et al. 1994). Therapeu- tic regimens containing beta-lactam antibiotics should therefore be able to select for PNSP, especially if given in low dosages. Clinical studies from France also support this theory (Guillemot et al. 1998). Modifying (increasing) the dose and duration of antibiotic therapy may therefore potentially limit the spread of resistant pneumococci as shown in another study (Schrag et al. 2001). Although it was not part of our prospective epidemiological study we confirmed that prescribed antibiotic dosages did not change between the first two phases of the study (II) and such change was unlikely between the second and third phases when antimicrobial use decreased much less than between the first phases. 62 In a Swedish study, a median duration of PNSP carriage (MIC, > or = 0.5 mg/L) was 19 days (range 3-267 days), but it was 10 days longer in infected than in asymptomatic contact cases (Ekdahl et al. 1997). A significant risk factor for prolonged carriage was repeated treatment courses for acute otitis media. Other significant risk factors for prolonged carriage were the occurrence of first episode of acute otitis media before the age of one year, the carriage of PNSP by other family members, and the obtainment of a first positive culture during the winter months (Ekdahl et al. 1997). In our studies most children carried PNSP 28-42 days after the last antimicrobial treatment. A rapid selection of PNSP isolates during or after (II) antibiotic treatment for acute otitis media specifically has also been shown in other studies (Dagan et al. 1998 a; Brook and Gober 2005; Mc- Cormick et al. 2005). The clinical outcome of antibiotic treatment of acute otitis media may depend on antibiotic-mediated bacterial eradication and the spread of resistant clones could be facilitated by failures to eradicate resistant strains and subsequent re-colonisation of the mucosal membranes after discontinuation of therapy (Dagan et al. 2001 b). Conversely, eradication of susceptible pneumococcus in the nasopharyngeal flora by antimicrobials means that new strains will emerge thereafter and hence may also increase the likelihood of new episodes of acute otitis media (recurrent otitis media) and possibly increase the risk of having tympanostomy tube later as described later on page 68-69.

Amount and type of antimicrobials associated with resistance in the community Although the prevalence of resistant strains can be related to the community use of antimicrobials, in most countries, it is often not possible to quantify this use. Accordingly, it has not been possible to define acceptable levels of antibiotics usage. In our study we have tried to quantify the use, especially among Icelandic children, from the prevalence of prescriptions, the number of defined daily doses/1000/day and the number of defined daily doses per prescription by antimicrobial class and residence (II). At the same time, we measured the resistance rate among pneumococci, and its relation to antibiotic usage. On the other hand, it was not our aim to analyse the 63 safety thresholds of use for either each antibiotic class or the total use. Low dosage and long duration of antimicrobial treatment has been demonstrated to increase the risk of PNSP carriage (Guillemot et al. 1998). Comparison of the number of DDD/prescription in 1993 and 1998 studies shows that this is not likely to be the explanation for differences in PNSP rate in the study areas (II). Our data suggest that some antimicrobial agents may be more active in inducing PNSP carrier state because of selective antimicrobial pressure. For example, only trimethoprim-sulfamethoxazole was significantly associated with carriage of PNSP in our first study (I). Other authors have also shown an association between trimethoprim-sulfamethoxazole and carriage of PNSP (Dagan et al. 1998 b; Melander et al. 1998) An explanation similar to that for increased carriage risk of PNSP by selective antimicrobial pressure after recent antimicrobial treatment may also apply to carriage of erythromycin-nonsusceptible strains of pneumococci (V). Much higher use of macrolides, especially azitromycin, in 2003 than in 1998 may be one explanation for this development. Even though the continued high use of antimicrobials in one area (area V) could perhaps explain why the PNSP of multiresistant serotype 6B (the Spain6B-2 clone) is still present in 2003, it is tempting to conclude that rapidly increasing use of azithromycin (one third of all prescriptions in 2003 and much higher than in the other areas) has established a favourable selective environment for this clone, which is also macrolide-nonsusceptible. This environment may also have led to the marked increase in the number of erythromycin-resistant but penicillin-susceptible pneumococci in that area. In fact, the long half-life and low serum concentrations of azithromycin have been associated with increased resistance rates of not only macrolide-nonsusceptible but also penicillin-nonsusceptible pneumococci (Kastner and Guggenbichler 2001; Dias and Caniça 2004). This is in accordance with what is now observed in many other countries as the hidden epidemic of macrolide-resistant pneumococci (Klugman and Lonks 2005). Our study (comparative and analytical covering 10 years) is one of the first clearly showing that there is an causative association be- 64 tween antimicrobial use and antimicrobial resistance patterns in different communities, something which had previously been shown in hospital settings (McGowan 1983) and day-care settings (Reichler et al. 1992). A recent French study showed also that intensive educational strategies aimed at optimizing antibiotic use could significantly reduce the rate of PNSP colonization in areas with high resistance rates (Guillemot et al. 2005). Results from studies in Sweden, Spain and Portugal dealing with the association between antimicrobial use and carriage of antimicrobial-resistant pneumococci are congruent with results from our studies in most aspects (Melander et al. 1998 a; Melander et al. 1998 b; Melander et al. 2000; Granizo et al 2000; Dias and Caniça 2004; García-Rey et al. 2004). Other older Swedish studies showed the emergence and persistence of ß-lactamase-producing bacteria (Hae- mophilus influenzae and Moraxella catharralis) in the upper respiratory tract in children treated with ß-lactam antibiotics (Molstad et al. 1988; Molstad and Hovelius 1989; Eliasson et al. 1990). This resistance pattern also appeared to be a long-term ecological effect of differences in the level of use of antibiotics between different communities in Sweden (Molstad et al. 1992).

Clonal spread in the community The first observation of a PNSP, multiresistant, serotype 6B in Iceland was in 1989 and in the following years proved to be strain recognised as the Spanish Icelandic clone, i.e., Spain6B-2 as mentioned earlier. Before the first phase of the study, this clone was the first to spread in the heavily populated metropolitan areas near Reykjavik, the capital of Iceland, and then spread to remote areas. Despite means for the fast transport of people, the transfer of new pneumococcal clones is highly time-dependent (Melander et al. 1998 b; Arason et al. 2002 a). In this study, special attention has been given to not only the fast spread of this clone in the community through high antimicrobial use but also its disappearance (V). The disappearance, however, was not explained, as might be expected, by direct (individual) association between antimicrobial use and carriage risk of PNSP in children, as discussed above. The effect of possible interaction of antimicrobial use and herd immunity may have been the missing explanatory link 65 in the first phase of the study. We have therefore studied the possible interplay of known individual risk factors for PNSP carriage in the communities, such as antimicrobial usage interacting with factors like time and the distance between study areas in the second and third phases of the study. The increase of PNSP of multiresistant serotype 6B studied in this study, shown to be phenotypically identical by antibiotic susceptibility testing to the Spain6B-2 clone, in “virgin” communities (E and B) in the second phase explains the fitness of that particular clone to spread even in communities with low antimicrobial use. The prevalence has decreased in all of the study areas (V) and, as far as I know, in Iceland as a whole. For this particular penicillin-resistant pneumococcal strain (clone), it can be postulated that the period from the onset to the end of an epidemic in small communities with low antimicrobial use is less than 10 years. In addition to herd immunity, it is likely that the extent of antimicrobial use will play a role in determining the peak prevalence (how fast this clone will spread through the community by high carrying rate by the individuals) and the subsequent endemic prevalence and behaviour. This led us to construct a theoretical model for a plausible explanation of the appearance and disappearance of this special bacterial clone, which is shown in Figure 25 b. It is reasonable to believe that other or new antimicrobial-resistant pneumococcal clones will behave in a similar manner. Strains failing to produce a polysaccharide capsule have commonly been isolated from carriage and disease contexts in some other studies (Hanage et al. 2006). Some studies seem to indicate that most non-typeable pneumococci may have diverse genetic back- grounds compared to typeable pneomococci and may have evolved as a distinct group of pneumococcal isolates (Sa-Leao et al. 2006; Hanage et al. 2006). The non-typeable pneumococci in our 2003 study (V) all had a rough appearance and are therefore probably non- encapsulated, although this has not been confirmed with molecular investigations. Such rough (non-encapsulated) strains had not been observed in the previous two studies. It is unlikely that such rough strains were missed in the previous studies since all the agar plates were read by the same two senior biomedical laboratory scientists. Their appearance therefore probably indicates the introduction of a 66

a) Area H Area V Area E and B 2 5

2 0

1 5 E B 1 0

0 1 9 9 3 1998 2 003 1 9 9 3 1 9 9 8 2 0 0 3 1 9 9 3 1 9 9 8 2 0 0 3

b) 2 5 Area V 2 0 Area E

1 5

Area H 1 0 Area B

0 1993 1998 2003 Fig. 25. a) Prevalence of penicillin-nonsusceptible pneumococci (PNSP) of multiresistant serotype 6B (recognised as the Spanish- Icelandic clone, Spain6B-2), as a percentage of all children carrying pneumococci, observed in areas H, V, E and B in the studies in 1993, 1998 and 2003. b) A theoretical model (epidemiological curves) for the spread and disappearance of Spain6B-2 clone in four communities in Iceland 1993-2003 (The form of the curves indicate that the time scale for the emergence of resistance under constant selective pressure is typically much shorter than the decay time (Austin et al. 1999)). novel clone. Probably the new non-typeable strains (clone) have appeared and spread successfully in the day care centres. This increase, however, has not been noted in specimens from infected patients in Iceland (Kristinsson K.G., personal communication), probably consistent with the lack of virulence of these strains. The significance of penicillin non-susceptibility in the non-typeable (non-encapsulate) pneumococci is not clear. 67 New typeable (encapsulated) as well as non-typeable (non-encapsulated) PNSP have become established in recent years in the study areas. The choice of antimicrobial class may influence the selective environment, favouring this particular resistant clone and stabilising the older ones. Also, in the near future, herd immunity may change through the impact of new pneumococcal conjugate vaccines (if used), which will probably reduce the acquisition of vaccine-type strains but increase the risk of non-vaccine serotype strain acquisition in the population.

Associations between acute otitis media, antimicrobial use and tympanostomy tube placements In the first part of our 1993 study, evaluation of risk factors for carriage of PNSP demonstrated that antimicrobial use was an important risk factor. Our results indicated that the use of trimethoprim-sulphamethoxazole might be worse than the use of other antimicrobials (I). This was followed by a nationwide campaign to reduce unnecessary antimicrobial use for upper respiratory tract infections, mainly in children as described earlier (Kristinsson 1999). These efforts resulted in a 35% reduction in the use of liquid antimicrobials for oral use by children from 1992 to 1997. This is in congruence with even bigger changes in one study area (area E), where the antimicrobial prescription for acute otitis media diminished by about 2/3 over the 10-year period, and broad-spectrum antimicrobials were only used in 32% of cases compared to 78% in the high-consumption area (IV). The most likely explanation, in my opinion, is a change in antimicrobial prescription habits for acute otitis media among the GPs in that particular area rather than diminished prevalence of the natural onset of acute otitis media in that area but not the others as discussed above in relation to total antimicrobial use. How conservative treatment strategy may possibly diminish the prevalence of acute otitis media will be discussed better in connection to the changes in the rate of tympanostomy placements for children here below (diminished rate of children who may develop chronic effusion or relapsing acute otitis media and who may need tympanostomy tubes later). An important question is also whether tympanostomy tubes will protect against new middle-ear infections, diminishing the need for antimicrobials later. Our results indicate that the wide-use of tympanostomy 68 tubes does not support this view. This does not exclude the possibility that a subgroup of infection-prone children with chronic middle-ear effusion might benefit from placement of tympanostomy tubes. An association was observed between individual previous prescriptions of oral antibiotics for acute otitis media among children with tubes. Furthermore, there was an association between overall community antimicrobial use for acute otitis media and the cumulative prevalence of tympanostomy tube placement among children in the community (IV). Of special interest was that the prevalence of tympanostomy tubes decreased in areas with decreasing use of antimicrobials for acute otitis media (IV). This observation, however, was only statistically significant in one area, between 1998 and 2003, although similar time trend changes were also observed for the other areas. This was also in accordance with parental attitude toward restrictive antimicrobial prescription policy. This phenomenon may have different underlying explanations. One possible causative correlation may be explained partly by the fact that children having tubes had got recent oral antimicrobials for acute otitis media more often than children not having tympanostomy tubes. This may be due to the fact that otorrhea is a common problem in children with tympanostomy tubes (Ah-Tye et al. 2001). This may lead to prescriptions of oral antibiotics due to suspicion of acute otitis media. In our study, we did not analyse the use of topi- cal antibiotics, such as ear-drops, that are also frequently used and recommended as a first line therapy in clinical guidelines for this problem. The possibility of a positive causative correlation between antimicrobial drug (over) use for acute otitis media, further episodes of acute otitis media and tympanostomy tube placement later may be explained in connection with changes in the microflora of the nasopharynx by antimicrobias. Three different scenarios can be postulated: 1. The majority of pneumococcal acute otitis media events may develop in association with newly acquired carriage of pneumococcus (Gray et al. 1980; Syrjanen et al. 2005). Eradica- tion of susceptible pneumococcus in the nasopharyngeal flora by antimicrobials means that new strains will emerge thereaf- 69 ter and hence may increase the likelihood of new episodes of acute otitis media. 2. A rapid selection of PNPS isolates during antibiotic treatment for acute otitis media as has been shown in some studies as mentioned earlier (Dagan et al. 1998 a; Brook and Gober 2005) or after treatment (Arason et al. 2002 a; McCormick et al. 2005) (See discussion on pages 60-62). 3. Frequent use of antimicrobial drugs probably leads to change in the bacterial flora in the community by promoting the emergence of resistant bacteria. This and no. 2 is associated with a decreased rate of successful eradication of pathogens from middle-ear fluid, which is associated with clinical failure, chronic middle-ear effusion and risk of relapsing acute ear symptoms (Reichler et al 1992; Dagan 2000; Brook and Gober 2005; Libson 2005) (See also discussion in the next chapter).

Another explanation for the correlation between antimicrobial use for acute otitis media and prevalence of tympanostomy tubes on community level may be non-causative. Differences in medical practice both for antimicrobial prescribing and threshold indications for tympanostomy placements among otitis-prone children and changes overtime because of intervention strategies to lower antimicrobial use in some practices as described earlier is one possible explanation of the correlation (Gabbay and le May 2004; Petursson 2005 a). It must also be kept in mind, although an unlikely explanation concerning our results in a small country that the incidence of respiratory tact infections may vary.

Acute otitis media in relation to antimicrobial-resistant bacteria Our results specifically show rapid selection of PNSP isolates after antimicrobial treatment because of acute otitis media, as has also been shown in other studies during treatment (Dagan et al. 1998 a; Brook and Gober 2005). This may increase the risk of treatment- resistant episodes of acute otitis media and chronic effusion in the middle-ear (Reichler et al. 1992; Dagan 2000; Brook and Gober 2005; Libson 2005) as mentioned above. One study in the 1970s, showed that when acute otitis media was treated with a broad-spec- 70 trum antibiotic, it relapsed more often than after a course of narrow- spectrum antibiotic (Howard et al. 1976). The incidence of recurrent acute otitis media increased three-fold in Finland from 1978/1979 to 1994/1995, at the same time as penicillin-V was replaced with broad-spectrum antibiotics as the first-line drug without any obvious change in microbial ecology that would justify the shift (Joki-Erkki- la et al. 2000). However, I can not draw any safe conclusion from our studies concerning the question of whether resistant bacteria increase the risk of new episodes of acute otitis media more often, compared with the risk of a new episode due to non-resistant bacteria.

Tympanostomy tubes and bacterial antimicrobial resistance The potential association between tympanostomy tube placements and antimicrobial resistance was not specifically studied. However, it may be concluded, in agreement with what was stated above about the associations between antimicrobial use and resistance and about antimicrobial use and tympanostomy tubes placements in the study areas, that there is probably a indirect association between tympanostomy tube placements and the prevalence of bacterial antimicrobial resistance in the community (see discussion above). Our results, however, do not support a conclusion that frequent use of tympanostomy tubes protects against antimicrobial resistance.

Limitations in the study design I have mentioned some strengths of our studies, one being that it is based on subjects from different well-defined communities, allowing conclusions, based on the population level as well as differences in clinical practice in Iceland. However, the study samples are limited as they are focused on pre-school children, and also limited to antimicrobial use, mostly because of diagnosed upper respiratory tract and middle-ear infections by GPs in primary healthcare settings. Diagnosis of precise acute otitis media can be hard to define and differ also by national perspectives and specialty (Rosenfeld 2002). A child with a bacterial upper respiratory tract infection often has a clinical picture of symptoms involving more than one site, including the middle-ear, nose and throat. One diagnosis (acute otitis media) may therefore be used more often than others as a primary reason for 71 antimicrobial prescription among GPs in ordinary clinical settings when prescribing antimicrobials is deemed to be needed. Further- more, only bacteria from the nasopharynx have been cultured, and the culturing of bacteria has focused on pneumococci. This makes it impossible to conclude anything about adults, other infections, and bacteria other than pneumococci and the resistance patterns of bacteria other than pneumococci. On the other hand, this focus on a specified population, specified infections and a specific bacterium may also be a strength as confounding factors can be expected to be less important. In our studies we used antibiotic susceptibility testing together with serotyping to characterise the bacterial isolates of pneumococci as a phenotypes. Although it is probably true that PNSP of multiresistant serotype 6B are members of the Spain6B-2 clone, antibiotype and serotype alone are not enough to draw a definitive conclusion. Molec- ular methods, such as pulsed-field gel electrophoresis and multilocus sequence typing for DNA fingerprinting would be the only methods suitable for drawing a definitive conclusion about the clonal origin of the multiresistant 6B strain to the Spain6B-2 clone. The non-typeable pneumococci in the 2003 study (V) all had a rough appearance and are therefore probably non-encapsulated, although this has not been confirmed with molecular investigations. A clonal origin for this nontypeable pneumococci is therefore also hard to define.

Summary of associations studied Figure 4 shows some potential associations analysed in this thesis. These potential associations have been discussed, and Figure 26 summarises this discussion. Recent antimicrobial use is the most consistent and important risk factor for the carriage of resistant pneumococci at each time (I, II, V), and the choice of antimicrobial class may influence the selective environment, favouring particular resistant clones (I, V). It seems that age was strongly associated with the carriage of PNSP in the first study but not at all in the third one. Neither did gender (I, II V), number siblings (I, II, V), day care (I, II, V), history of tympanostomy tubes (II, V), presence of an upper respiratory tract infection (I) and smoking in the household of the index child (V). 72

Antimicrobial use for acute otitis media

Antimicrobial resistance Total development antimicrobial use among pneumococci (spread ) selection) ( Tympanostomy tube placement ) Parental ( view

Fig. 26. Conclusions concerning potential associations and their directions.

An association was observed between individual previous prescriptions of oral antibiotics for acute otitis media and younger age, living in a high antimicrobial consumption area and among children with tubes (IV), between day care attendance and children having tubes (IV) and between overall community antimicrobial use for acute otitis media and the cumulative prevalence of tympanostomy tube placement among children in the community (IV). Parents’ expectations of antimicrobial prescriptions for their child because of acute otitis media were associated with former antimicrobial use (III) and by living in area with high antimicrobial utilization (III, IV). A bidirectional arrow means that our studies provide some direct (causative) or indirect (non-causative) support for such a relationship, and a bracketed arrow means that there is a probable association, although one not covered by our studies. As far as I know, this is the first time that such associations for 73 these subjects have been studied in the general population. However, I am well aware that our data can never allow final conclusions concerning causal relationships between the factors studied. 74 SUMMARY OF AIMS, MAIN RESULTS AND CONCLUSIONS

Some specific aims were stated in the introductory chapter. They are repeated below along with the relevant main findings from our studies.

• To describe the total use of antimicrobials in the communities, specifically among pre-school children, by class of antimicrobials, amount prescribed and prescription rate in selected, well-defined communities. Repeated cross-sectional studies have enabled us to observe possible trends over time regarding antimicrobial use over a 10-year period. Prudent antimicrobial use was encouraged, especially for upper respiratory tract infections and acute otitis media. The number of antimicrobial courses prescribed to pre-school children diminished markedly, especially for acute otitis media, but varied between study areas, indicating that in areas where the prescription rate is high, GPs prescribe broad-spectrum antimicrobials relatively more often than narrow-spectrum antimicrobials.

• To describe potential links between antimicrobial treatment for acute otitis media, socio-demographic factors and parental views on the use of antimicrobials. The child’s age and residence were independently associated with the number of treatments for acute otitis media. Parents’ expectations of antimicrobial prescriptions for common colds were associated with the doctor’s handling of upper respiratory tract infections. It is concluded that antimicrobial prescriptions may be more common in areas where parents have such expectations.

• To describe the use of tympanostomy tube placements and possible association with the use of antimicrobials among children. The cumulative prevalence of tympanostomy tube placements among pre-school children is very high in Iceland (over 30%). An association was observed on the community level between 75 the prescription of oral antimicrobials, specifically for acute otitis media, and the cumulative prevalence of tympanostomy tube placements. Of special interest was the observation that the prevalence of tympanostomy tubes decreased significantly in areas where the use of antimicrobials for acute otitis media decreased, and increased where the use of antimicrobials was highest. The possibility of a causative, positive correlation between antimicrobial drug (over)use for acute otitis media, future episodes of acute otitis media and tympanostomy tube placement later, warrants further investigation. Differences in routine medical practice may be a possible non-causative explanation of the correlation.

• To analyse associations between antimicrobial use and nasopharyngeal carriage of PNSP in children with regard to both individual use and total use in the community. There was a strong association between antimicrobial use on an individual level and the nasopharyngeal carriage of PNSP in all three phases of our studies. The results indicate that this association cannot be solely explained by (selective) antimicrobial pressure on penicillin-susceptible strains. It is proposed that “selective acquisition” of (foreign) non-susceptible strains from the outer ecosystem together with unmasking of dormant and/or nonsusceptible strains present in very low numbers from the inner ecosystem could also be a possible explanation. Nevertheless, the interplay between antimicrobial use on a community level and clonal spread of non-susceptible pneumococci is harder to explain (see next paragraph).

• To describe the clonal spread of PNSP in communities and analyse the interplay of factors contributing to this spread. The PNSP strain of multiresistant type 6B (phenotypically identical by antibiotic susceptibility testing to the Spain6B-2 clone) appeared and disappeared over a 10-year period in the communities, both in communities with high and low antimicrobial use. This probably reflects the strain’s fitness to spread where herd immunity of the population is lacking. We conclude that the spread of resistant clones within well-defined areas seems to follow a 76 classical “rise and fall” epidemiological pattern. The extent of antimicrobial use may determine both the peak prevalence and the subsequent endemic prevalence in the community. The choice of antimicrobial class may influence the selective environment, favouring particular resistant clones. 77 CLINCAL IMPLICATIONS

The prescription of antimicrobials for children has decreased considerably in some of the study communities, particularly prescriptions for acute otitis media. In some areas the decrease is dramatic. I believe that GPs in some of the areas studied greatly changed their prescription patterns for antimicrobials immediately after the first phase of this study in 1993 because of the study’s findings regarding the risk of development of bacterial resistance in the community. Antimicrobial use for acute otitis media, however, is still about 50% of all antimicrobial prescribing today for children in Iceland. In some areas the parents are well informed about the consequences of uncritical antimicrobial use, and in these areas the parents are also more prepared to wait before starting antimicrobials for their children. This indicates the importance of getting information to parents about the appropriate management of infectious diseases, especially in cases of mild symptoms because of acute otitis media. The use of tympanostomy tubes is commoner in Iceland than in other comparable countries. Our studies indicate that the use of tympanostomy tubes does not lead to less use of antimicrobials, either in children as a whole or, specifically, in the children with a current history of tympanostomy tubes. Our results also demonstrate an association between the use of antibiotics and use of tympanostomy tube placements. However, it is impossible to say whether this association is due to causal effects or differences in the routine medical practice or both. These observations may warrant further discussion on optimal treatment to achieve a consensus on such treatment of middle-ear infections and other upper respiratory tract infections. For small communities the spread of resistant clones appears to be the main reason for rapid and significant changes in pneumococcal resistance rates. Herd immunity against new strains of PNSP seems to appear within a certain period, even where the consumption of antimicrobials is high. The extent of antimicrobial use may determine both the peak prevalence and the subsequent endemic prevalence in the community. Recent antimicrobial use by direct (selective) antimicrobial pressure on susceptible strains, “selective acquisition” of 78 (foreign) non-susceptible strains from the community and unmasking of dormant non-susceptible strains present from the inner ecosystem, is the most consistent and important risk factor for carriage of these resistant strains. Associated with a decreased rate of successful eradication of pathogens from middle-ear fluid because of antimicrobial resistance among them is a tendency toward chronic middle-ear effusion and risk of relapsing acute ear symptoms. The positive effect of decreased antibiotic use on antibiotic resistance may outweigh the possible benefit of earlier symptom resolution attributed to antibiotic treatment in the case of mild acute otitis media. Eradication of the susceptible pneumococcus in the nasopharyngeal flora and interference on the natural balance of microbial species in the nasopharynx by antimicrobials means that new strains will emerge thereafter and hence may also increase the likelihood of new episodes of acute otitis media. “Preventing recurrent acute otitis media is a goal of child healthcare. The objective is to reduce the frequency of pain and fever because of otitis media, shorten the duration of hearing loss, reduce the costs of physician visits, surgery and drugs, reduce parent anxiety and prevent long-term sequelae” (Giebink 2000). Identification of risk factors for acute otitis media and antimicrobial-resistant pneumococcal colonisation of the nasopharynx together with the possible use of the new protein-polysaccharide conjugate pneumococcal vaccine against the most potential pathogenic strains of pneumococci, although it has not yet been used in Iceland, provides new opportunities for preventing and managing acute otitis media and other pneumococcal diseases among children in the future. Efforts to improve the judicious use of antimicrobials for acute otitis media should focus on improving diagnostic accuracy. There is also a need to use qualitative methods to prepare information and to understand factors influencing behavioral change among antimicrobial prescribers. Our results indicate that the uncritical use of antibiotics increases the risk of developing antimicrobial resistance. Therefore, prudent use of antimicrobials is recommended. 79 REFERENCES

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PAPER I

Do antimicrobials increase the carriage rate of penicillin resistant pneumoco... Arason, Vilhjalmur A; et al British Medical Journal; Aug 17, 1996; 313, 7054; Health Module pg. 387

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101

PAPER II

MICROBIAL�DRUG�RESISTANCE Volume�8,�Number�3,�2002 © Mary�Ann�Liebert,�Inc.

Clonal�Spread�of�Resistant�Pneumococci� Despite�Diminished�Antimicrobial�Use

VILHJALMUR�A.�ARASON,1 ADALSTEINN� GUNNLAUGSSON,2 JOHANN� A.�SIGURDSSON,1 HELGA�ERLENDSDOTTIR,2 SIGURDUR�GUDMUNDSSON,3 and�KARL�G.�KRISTINSSON2

ABSTRACT

The�effects�of�community-wide�interventions�to�reduce�resistance�rates�are�poorly�understood.�This�study�evaluated�the�effect�of�reduced�antimicrobial�usage�on�the�spread�of�penicillin-nonsusceptible�pneumococci�(PNSP) in�four�communities�in�Iceland.�The�study�was�performed�after�interventions�to�reduce�antimicrobial�usage and�compared�to�an�identical�study�performed�5�years�before.�A�randomized�sample�of�953�children�was�chosen�from�all�2,900�1-�to�6-year-old�children�living�in�four�well-defined�communities.�The�main�outcome�measures�were�nasopharyngeal�carriage�of�PNSP�and�individual�and�community�use�of�antimicrobials.�Pneumo- cocci�were�carried�by�51.7%�of�the�743�children�enrolled,�and�8.1%�of�the�pneumococci�were�PNSP�as�opposed to� 8.5%� in� the� previous� study.� The� antimicrobial� use� of� participants� had� been� reduced� from� 1.5� to� 1.1 courses/year�and�the�overall�use�among�children�,7�years�old�living�in�the�study�areas�from�13.6�to�11.1�defined�daily�dosages/1000�children�per�day.�The�prevalence�of�PNSP�increased�in�the�two�areas�furthest�away from�the�capital�area�despite�reduced�consumption.�The�major�risk�factors�for�carriage�of�PNSP�remained the�same.�Interventions�can�be�effective�in�reducing�antimicrobial�use.�Pandemic�multiresistant�clones�can also�spread�fast�in�small�communities�with�low�antimicrobial�use,�where�their�appearance�may�be�delayed compared�to�highly�populated�urban�areas.�Clonal�spread�and�herd�immunity�are�important�factors�to�be considered�in�the�evaluation�of�intervention�effects.

INTRODUCTION This�was�followed�by�a�nationwide�campaign�to�reduce�unnecessary�antimicrobial�use�for�upper�respiratory�tract�infections, 9 OMPARATIVE AND ANALYTICAL STUDIES have�demonstrated mainly�in�children. The�interventions�consisted�both�of�infor- Ca�relationship�between�high�antibiotic�consumption�and�in- mation�and�education�of�the�public�through�mass�media�and�of creasing�drug�resistance.�This�correlation�has�been�found�both physicians�through�meetings�and�the�Icelandic�Medical�Jour- for�individual�antimicrobial�use1,13 and�antimicrobial�use� by nal. New�antimicrobial�prescription�guidelines�were�prepared whole�communities.1,15–17 However,�the�effect�of�reduced�an- and�made�available�on�the�Internet.�Prudent�antimicrobial�use timicrobial�consumption�on�the�prevalence�of�resistance�has�not was� encouraged,�especially�for�upper�respiratory�tract� infec- been�clearly�documented�on�a�community�wide�scale. tions.�These�efforts�resulted�in�a�35%�reduction�in�the�use�of The� incidence� of� penicillin-nonsusceptible� pneumococci liquid�antimicrobials�for�oral�use�by�children�from�1992�until (PNSP)� increased�rapidly�in� Iceland�from� 19896 until�1993, 1997�(data�from�the�Ministry�of�Health).�Subsequently�the�over- when�it�had�reached�20%�in�pneumococcal�infections.7 Most�of all�incidence�of�PNSP� in�pneumococcal�infections�in�Iceland the�PNSP�belonged�to�a�single�multiresistant�serotype�6B�clone declined�to�12%�in�1997.2,9 (the�Spanish-Icelandic�clone,�Spain-26B).18 A�study�performed There�are�many�factors�other�than�antimicrobial�use�that�can in�1993�to�evaluate�risk�factors�for�carriage�of�PNSP�demon- play�a�role�in�the�spread�of�PNSP.8 The�interplay�between�these strated�that�antimicrobial�use�was�an�important�risk�factor,�and risk�factors�may�be�complex�and�is�poorly�understood.�Studies suggested�that�the�use�of�trimethoprim-sulfamethoxazole�and evaluating�this�interplay�in�the�community�are�urgently�needed macrolides�might�be�worse�than�use�of�other�antimicrobials.1 to�assist�public�health�officials�in�designing�effective�interven-

1Department�of�Family�Medicine,�University�of�Iceland,�Solvangur,�Hafnarfjordur,�Iceland. 2Department�of�Clinical�Microbiology,�Landspitali�University�Hospital,�Reykjavik,�Iceland. 3Directorate�of�Public�Health,�Reykjavik,�Iceland.

187 188 ARASON�ET�AL. tion�strategies�to�curtail�the�rapidly�increasing�resistance�rates. The�sites�were�visited�in�April�and�May,�1998�(same�time�of The�confined�Icelandic�community�is�ideal�for�such�studies.�To the�year�as�in�the�1993�study).�After�informed�parental�consent, get�a�better�understanding�of�the�interplay�of�risk�factors�and a�nasopharyngeal�specimen�was�taken�from�each�child.�Parents time,�the�aim�of�this�study�was�to�analyze�the�effect�of�dimin- were�asked�to�bring�their�child�to�the�local�health�center�or�the ished�antimicrobial�use�on�individual�risk�factors�and�the�preva- sample�was�obtained�at�the�relevant�day�care�center.�The�par- lence�of�PNSP�in�the�same�communities�as�were�studied�in�Ice- ents�were�also�asked�the�following�questions�regarding�antimi- land�in�1993.1 crobial�use�of�their�child:�number�of�antimicrobial�courses�in the�preceding�year;�the�date�and�type�of�the�last�antimicrobial agent�used;�type�of�infection�and�whether�the�child�had�been MATERIALS�AND�METHODS taking�prophylactic�antibiotics�$3�weeks�during�the�preceding year.�The�same�information�was�also�collected�from�the�med- Study�population�and�design ical�records�at�the�local�health�center.�Children�that�had�received antimicrobial�treatment� in� the� preceding�2� weeks� were� ex- Four�of�five�geographical�areas�that�had�been�studied�in�a cluded,�as�in�the�previous�study. 1 comparative�study�in�1993 could�be�re-examined�in�1998.�At The� National�Bioethics�Committee�and�the�National�Data the�end�of�1997�(December�1,�1997),�these�areas�had�a�total Protection�Commission,�Iceland,�approved�the�study. population�of�27,013,�including�2,900�children�from�1�to�6�years old,�e.g., Hafnarfjordur�(H),�18,203�inhabitants,�1,989�children Microbiology 1–6�years�old.�Corresponding�figures�for�the�other�areas�were: Vestmannaeyjar�(V),�4,640�and�512;�Egilsstadir�(E),�3,076�and Nasopharyngeal�samples�were�obtained�with�a�rayon-tipped 300;�and�Bolungarvik�(B),�1,094�and�99.�Area�H�is�a�town�ad- swab�(Mini-tip�Culturette®,�Becton�Dickinson�and�Co.,�Sparks, jacent�to�the�capital�(Reykjavik),�area�V�a�fishing�town�on�an MD),�stored�for�maximum�of�24�hr�before�they�were�inoculated island�of�the�south�coast,�area�E�a�town�surrounded�by�a�large on�two�blood�agars�(Difco,�Detroit,�MI)�one�containing�gen- farming�area,�and�area�B�a�fishing�town�(Fig.�1).�The�popula- tamicin�(5�mg/L)�and�incubated�anaerobically�and�the�other�in- tion�density�and�living�standards�are�similar�in�all�the�study cubated�aerobically�with�added�CO2.�Colonies�were�identified towns.�The�study�population�was�chosen�to�allow�a�representa- with� conventional�methods,�and�pneumococci�were�screened tive�comparison�with�the�1993�study�performed�in�these�areas. for�penicillin�resistance�by�the�oxacillin�disc�diffusion�test19 and After�computer�randomization�of�all�1-�to�6-year-old�children the�MIC�of� nonsusceptible�isolates�determined�by�the�E-test identified�from�the�National�Registry�of�these�areas,�953�chil- (AB�Biodisk,�Solna,�Sweden)�according�to�the�manufacturer’s dren�(33%�of�the�children�of�that�age)�were�selected�for�par- recommendations.�Susceptibility�to�erythromycin,�tetracycline, ticipation�(H,�20%;�V,�58%;�E,�63%;�and�B,�62%).�Seventeen chloramphenicol,�and�trimethoprim-sulfamethoxazole�was�de- general�practitioners,�of�whom�14�were�the�same�as�in�the�1993 termined�by�disc�diffusion�tests�according�to�the�NCCLS�meth- study,�served�these�areas. ods� and� criteria.5 Penicillin� nonsusceptible� isolates� were

FIG.�1. Map�of�Iceland�showing�the�major�roads,�Reykjavik,�Akureyri,�and�the�study�sites. ANTIMICROBIAL�USE�AND�CLONAL�SPREAD 189 serotyped�by�co-agglutination11 using�antisera�from�the�State RESULTS Seruminstitute�(Copenhagen,�Denmark).�Antimicrobial�suscep- tibilities�to�other�antimicrobials�were�tested�by�disc�diffusion Nasopharyngeal�carriage� tests�using�the�NCCLS�methods�and�criteria.5 Of�the�953�children�invited�to�participate,�743�(78%)�participated�(H,�301,�75%;�V,�224,�76%;�E,�167,�88%;�and�B,�51, Antimicrobial�sales 83%)�and�384�(52%)�carried�pneumococci.�The�pneumococcal Information�on�total�antimicrobial�sales�(adults�and�children) carriage�rate�varied�from�37%�to�58%�(H,�58%;�V,�54%;�E, was�collected�from�computerized�records�of�the�local�pharma- 41%;�and�B,�37%).�The�mean�age�for�the�whole�group�was�4.2 cies�in�the�study�areas�for�the�12�months�preceding�the�study years�(95%�CI�4.1–4.3)�and�the�age�ranged�from�1�to�6�years visits�(May,�1997,�to�April,�1998).�The�sales�were�assumed�to [V,� 4.2� (4.0–4.5);� B,� 4.2� (3.8–4.7);� E� 4.1� (3.8–4.4);� H� 4.2 represent�the�antimicrobial�use�and�calculated�in�number�of�de- (4.0–4.4)]. fined�daily�doses�per�1,000�inhabitants�per�day�(DDD/1000�in- The�proportion�of�pneumococci�that�was�nonsusceptible�to habitants�per�day).21 In�addition,�the�antimicrobial�sales�for�the penicillin�was�8.1%�and�all�of�the�nonsusceptible�strains�except age�group�0–6�years�were�analyzed�separately�by�looking�at�the two�were�multiresistant�and�of�serotype�6B�(i.e.,�phenotypically amount�prescribed�of�the�major�antimicrobial�classes�and�the identical�to� the�Spanish–Icelandic�clone).18,20 These�multire- amount�in�each�prescription�(calculated�as�the�mean�number�of sistant�strains�were�found�in�all�study�areas�and�their�penicillin DDDs�per�prescription). MICs�were�the�following:�one�strain,�0.125�mg/L,�21�strains 0.5�mg/L,�six�strains�1.0�mg/L,�and�one�strain�2.0�mg/L.�The Statistical�analysis two� other� strains� were� only� found� in� area� H;� one� was� of serogroup�9�(MIC�1�mg/L)�and�the�other�of�serogroup�19�(MIC The�single�outcome�variable�was�carriage�of�PNSP�penicillin- 0.5� mg/L),� both� resistant� to� trimethoprim-sulfamethoxazole. susceptible�pneumococci�(PSP).�The�variables�of�sex,�age,�area There�was�a�marked�difference�between�the�resistance�rates�of of�residence,�siblings,�day�care�attendance,�the�last�antimicro- the�study�areas,�with�rates�ranging�from�4.1%�to�18.8%.�The bial�agent�used,�2–7�or�8–52�weeks�from�last�antimicrobial�treat- rates�had�also�changed�significantly�from�the�1993�rates�(Table ment,�the�number�of�courses�in�the�preceding�12�months,�and 1),�with�reduced�resistance�rates�in�the�two�areas�located�in�the use�of�prophylactic�antibiotics�were�examined�for�association southwest�(H�and�V),�but�an�increased�rate�in�the�two�areas�fur- with�the�outcome�variable.�The�Fisher’s�exact�tests�were�used thest�away�from�the�capital�area�(B�and�E).�PNSP�were�found for� univariate�analysis�of� categorical�variables�and� one-way in�all�day�care�centers�in�area�E.�The�PSP�were�all�susceptible analysis�of�variance�(ANOVA)�for�continuous�variables. to�chloramphenicol�and�nonsusceptibility�to�erythromycin�and Multivariate� logistic� regression� by� backward� stepwise tetracycline�remained�uncommon�in�these�strains�(Table�2).�All method�was�used�to�estimate�the�risk�of�carrying�PNSP�to�con- PNSP�were�nonsusceptible�to�trimethoprim-sulfamethoxazole, trol� interdependence.� Individual�regression�coefficients�were and�approximately�one-quarter�of�the�PSP. tested�with�the�Wald�statistic,�and�confidence�intervals�calculated�for�the�odds.�The�multivariate�analyses�were�performed Antimicrobial�use with�the�SPSS® program�for�Windows�(Advanced�Statistics�Re- lease�8.0,�SPSS�Inc,�Chicago,�IL).�The�level�of�statistical�sig- By�the�whole�population�in�the�study�areas: In�1998,�a�total nificance�was�taken�as�0.05. of�15,153�antimicrobial�prescriptions�were�dispensed�to�the�in-

TABLE 1. CARRIAGE OF PNEUMOCOCCI (PNC)�AND PNSP� AND THE NUMBER OF ANTIMICROBIAL (AM)�COURSES PER YEAR IN THE STUDY GROUPS

DDD/1000�children�,7�yrs/day DDD/prescription No. No. No. AM�courses�per Area Year children PNC�(%) PNSP (%) year�(95%�CI) Total PEN AMP ERY SXT PEN AMP ERY SXT

H 1993 527 280�(53.1) 24�(8.6)a 1.5�(1.4–1.7) 11.9 2.2 7.0 0.5 2.2 3.7 4.4 2.7 2.4 1998 301 174�(57.8) 11�(6.3)a 1.0�(0.8–1.1) 9.9 1.3 7.3 0.5 0.8 3.7 4.4 2.5 2.8 V 1993 100 55�(55.0) 10�(18.2)a 1.7�(1.2–2.1) 23.2 3.5 9.7 2.9 7.1 3.6 4.2 3.0 2.4 1998 224 122�(54.5) 5�(4.1)a 1.4�(1.1–1.6) 17.1 1.8 13.0 0.9 1.4 4.5 4.3 2.7 2.5 E 1993 111 52�(46.8) 1�(1.9)a 1.3�(1.0–1.6) 13.4 2.4 7.0 0.5 3.5 4.6 3.9 3.3 2.3 1998 167 69�(41.3) 13�(18.8)a 0.9�(0.7–1.1) 7.6 1.2 5.2 0.2 1.0 3.7 4.4 2.8 2.4 B 1993 53 39�(73.6) 1�(2.6)a 1.5�(1.0–2.0) 9.6 2.5 4.3 0.6 2.2 3.2 4.1 2.7 2.1 1998 51 19�(37.3) 2�(10.5)a 1.0�(0.6–1.4) 8.3 0.5 5.9 0.0 1.9 5.0 3.4 — 2.0 Total 1993 791 426�(53.9) 36�(8.5)a 1.5�(1.4–1.6) 13.6 2.5 7.3 0.8 3.0 3.7 4.3 2.9 2.4 1998 743 384�(51.7) 31�(8.1)a 1.1�(1.0–1.2) 11.1 1.3 8.3 0.5 1.0 3.9 4.3 2.6 2.6

ap , 0.01. The�corresponding�figures�from�the�1993�study�are�shown�for�comparison.�The�use�of�the�main�antimicrobial�classes�(in�defined�daily�dosages�[DDD];�penicillin�[PEN],�ampicillin�[AMP],�trimethoprim-sulfamethoxazole�[SXT],�and�erythromycin�[ERY]) by�children�,7�years�old�living�in�the�study�areas�is�shown�on�the�right-hand�side,�together�with�the�mean�number�of�DDDs�per perscription. 190 ARASON�ET�AL.

TABLE 2. NUMBER OF PNEUMOCOCCI NONSUSCEPTIBLE (RESISTANT OR INTERMEDIATE)�TO ERYTHROMYCIN (ERY), TETRACYCLINE (TET),�CHLORAMPHENICOL (CHL),�AND TRIMETHOPRIM-SULFAMETHOXAZOLE (SXT),� ACCORDING TO DISC DIFFUSION TESTS,�IN 1993�AND 1998,�IN THE RESPECTIVE AREAS No. No. No. No. Area Year ERY (%) TET (%) CHLO (%) SXT (%)

H PSP 1993 0 0 1 3.0 0 0 62 24.4 1998 1 0.6 1 0.6 0 0 46 28.8 PNSP 1993 20 83.3 22 91.7 13 81.3 24 100 1998 7 63.6 8 72.7 8 72.7 11 100 V PSP 1993 2 4.4 2 4.4 0 0 17 37.8 1998 0 0 0 0 0 0 25 20.7 PNSP 1993 9 90.0 9 90.0 10 100 10 100 1998 5 100 5 100 5 100 5 100 E PSP 1993 0 0 0 0 0 0 12 23.5 1998 4 7.1 2 3.6 0 0 10 17.9 PNSP 1993 1 100 1 100 1 100 1 100 1998 13 100 13 100 13 100 13 100 B PSP 1993 0 0 0 0 0 0 6 15.8 1998 2 11.8 2 11.8 0 0 12 70.6 PNSP 1993 1 100 1 100 1 100 1 100 1998 2 100 2 100 1 50.0 2 100 Total PSP 1993 2 0.5 3 0.8 0 0 97 25.0 1998 7 2 5 1.4 0 0 93 26.6 PNSP 1993 31 86.1 33 91.6 25 69.4 36 100 1998 27 87.1 28 90.3 27 87.1 31 100

habitants�of� the�target�areas�by� the�local�pharmacies,�corre- timicrobial� agent� (50.1%)� but� not� in� 1998� (11.8%)� (p 5 sponding�to�14.2�DDD/1000�inhabitants�per�day�in�area�H,�17.2 0.0001). in�area�V,�12.3�in�area�E�and�11.5�in�area�B.�Of�these,�3,347 (22.1%)�were�for�children�under�7�years�old.�Compared�to�the Factors�associated�with�carriage�of�PNSP 1993�study,�antimicrobial�consumption�had�diminished�in�all study�areas�both�as�measured�in�defined�daily�doses�(14–43%) By�univariate�analysis,�young�age�(p 5 0.013),�geographical and�as�number�of�antibiotic�treatment�courses�per�year�(9–50%). location�(area�E;�p 5 0.003),�prophylactic�antimicrobial�treat- The�greatest�reduction�was�seen�in�area�E�(Table�1).�Children ment�(p 5 0.008),�antimicrobial�treatment�for�otitis�media�(p 5 in�area�V�still�consumed�around�50%�more�antimicrobials�than 0.001),�total�number�of�antimicrobial�treatment�courses�(p , children�in�the�other�areas.�The�reduction�in�antimicrobial�use 0.0001),�and�,8� weeks�from� last�antimicrobial�course�(p 5 was�greater�for�trimethoprim-sulfamethoxazole�than�for�other 0.002),�were�significantly�associated�with�PNSP�carriage.�The antimicrobials.�In�three�of�the�areas�(H,�V,�and�B),�there�was�a PNSP� carriage�rate� was� 21.6%� (11/51)� 2–7� weeks� after� an- slight�increase�in�the�use�of�broad-spectrum�penicillins�(mainly timicrobial�treatment�compared�to�5.6%�(8/142)�8–52�weeks�af- amoxycillin� and� amoxycillin� with� clavulanic�acid).� Overall, ter�treatment�(p 5 0.002)�or�6.3%�(12/191)�if�no�treatment�had there�was�no�change�in�the�number�of�DDDs�per�prescription, been�received�(p 5 0.001).�The� same� risk� factors� were� also and�there�were�only�relatively�small�changes�within�the�areas identified�in�the�1993�study,�but�not�the�same�geographical�lo- with�one�exception.�In�area�B,�there�was�almost�a�50%�increase cations.�Factors�that�were�not�found�to�be�significantly�associ- in� the�average�amount�prescribed�for�narrow�spectrum�peni- ated�with�PNSP�carriage�were�gender,�number�of�siblings,�day cillins�(mainly�phenoxymethylpenicillin)�(Table�1). care�attendance,�and�antimicrobial�courses�for�tonsillitis�and�si- By� the� study�population�alone: The� mean�number�of� an- nusitis.�The�numbers�were�too�small�to�assess�the�risk�of�indi- timicrobial�courses�per�child�in�the�study�population�was�1.1 vidual�antimicrobial�classes. during�the�year�preceding�the�sampling�(95%�CI�1.0–1.2).�This To�control�for�confounding�factors,�all�significant�variables was� a� 26.7%�reduction�compared�to� comparable�data�of� the from�the�univariate�analysis�were�used�in�a�multivariate�back- 1993�study�(Table�1).�Forty�percent�of�the�children�(298)�had ward� stepwise�logistic�regression�model.�Number� of� antimi- received�antimicrobials�at�least�once�during�the�preceding�year, crobial�treatments�and�geographical�area�(area�E)�were�the�only compared�to�65%�in� 1993.�In� both�1993�and�1998,�the�con- independent�risk�factors�for�carriage�of�PNSP�(Table�3). sumption�was�lowest�in�area�E�and�highest�in�area�V.�Acute�otitis�media�was�still�by�far�the�most�common�reason�for�antimicrobial� prescriptions,� constituting� 55%� of� all� antimicrobial DISCUSSION prescriptions�(65%�in�1993).�The�number�of�treatments�for�otitis�media�per�child�had�diminished�from�1.0�(95%�CI�0.9–1.1) The�nationwide�campaign�to�reduce�unnecessary�antimicro- in�1993�to�0.6�(0.5–0.7)�in�1998.�In�1993�trimethoprim-sulf- bial�use�for�upper�respiratory�tract�infections�in�children�that amethoxazole�was�the�most�commonly�recently�prescribed�an- took�place�between�1993�and�1998�was�associated�with�a�sig- ANTIMICROBIAL�USE�AND�CLONAL�SPREAD 191

TABLE 3. RISK (ODDS RATIO)�OF CARRYING PNSP� AS OPPOSED TO PSP� BY BACKWARD STEPWISE LOGISTIC REGRESSION METHOD

Variable Number OR 95%�CI p value

Residence Area�H 170 1�(reference�area) Area�V 122 0.519 0.17–1.620 0.2600 Area�E 67 4.139 1.65–10.39 0.0030 Area�B 19 1.852 0.36–9.500 0.4600

Number�of�antimicrobial 378 1.50 1.23–1.820 0.0001 treatments

Overall�significance:�x2 5 25.49,�df�5 4,�p�, 0.0001.

nificant�reduction�in�antimicrobial�use�by�children�in�the�study published�data).�The�PNSP�6B�prevalence�in�areas�E�and�B�was areas�(from�13.6�to�11.1�DDD/1000�children�,7�years�old�per very�low�in�1993�(1.9�and�2.6%;�one�strain�in�each�area)�com- day)�and�in�the�study�populations�(1.5–1.1�antimicrobial�courses pared�to�the�other�study�areas�and�they�are�also�furthest�away per�year).�This� reduction�was� mainly�due�to� reduced�use�of from�the�capital�area�(see�Fig.�1).�It�is�very�likely�that�it�took trimethoprim-sulfamethoxazole�and�fewer�prescriptions�for�oti- the�Spanish–Icelandic�clone�longer�to�reach�areas�B�and�E�than tis�media�(from�1.0�to�0.6�prescriptions�per�year).�Despite�this the�other�areas. reduction�in�antimicrobial�use,�the�proportion�of�PNSP�carriage Another� important� observation� is� the� high� prevalence only�declined�to�8.1%,�from�the�corresponding�figure�of�8.5%, reached�by�the�Spanish–Icelandic�clone�in�area�E�(18.8%),�an obtained�in�the�comparable�study�performed�in�1993.1 This�is area�with�low�and�declining�use�of�antimicrobials.�This�demon- in�contrast�with�the�much�greater�reduction�in�the�incidence�of strates�that�this�clone�can�also�spread�fast�in�communities�with PNSP�observed�in�specimens�submitted�from�patients�from�the low�antimicrobial�consumption,�which�probably�reflects�its�fit- whole�of�Iceland�(i.e., 20–13%),�where�the�majority�(.80%) ness�and�little�or�no�herd�immunity�of�the�population�in�that of�the�specimens�came�from�the�capital�area.8 In�the�1993�study, area. one�of�the�main�risk�factors�for�carrying�PNSP�was�recent�an- Low�dosage�and�long�duration�of�treatment�has�been�demon- timicrobial�use,1 yet�5�years�later�there�was�an�increasing�PNSP strated�to�increase�the�risk�of�PNSP� carriage.4 To�see�if�this prevalence�in�the�two�areas�that�not�only�had�the�lowest�use�of could�account�for�some�of�the�changes�in�PNSP�prevalence,�we antimicrobials�but�also�one�of�these�areas�had�the�greatest�recalculated�the�number�of�defined�daily�dosages�prescribed�per duction�in�their�use.�The�other�important�risk�factors�were�young prescription.�Comparison�of�the�number�of�DDD/prescription age�and�living�in�an�area�with�high�antimicrobial�consumption, (Table�1)�shows�that�this�is�not�likely�to�be�the�explanation�in but�the�age�distribution�of�the�children�in�these�populations�did the�study�areas.�Infection�control�measures�are�also�important not�change�between�the�study�periods.�Therefore,�an�important in�reducing�resistance�rates12 and�have�been�shown�to�be�ef- variable�is�likely�to�be�missing�from�the�risk�factor�analysis�in fective�in�reducing�antimicrobial�prescriptions�and�resistance�in the�previous�study.�Risk�factors�for�PNSP� carriage�that�have day�care�centers.3 Infection�control�was�not�part�of�the�Icelandic been�demonstrated�by�other�investigators�(day�care�center�at- intervention. tendance,�prior�hospitalization,�otitis-prone�condition,�otitis�me- One�of�the�major�strengths�of�this�study�is�the�use�of�ran- dia�not�responsive�to�antimicrobials,�white�race,�low�dose,�and dom� sampling� in� unselected�populations,�high� participation long�duration�of�antimicrobial�prescriptions)10 cannot�account rates,�and�the�quality�of�the�data�in�general.�The�number�of�par- for�these�differences. ticipants�was�just�over�one-quarter�of�all�1-�to�6-year-old�chil- How�can�the�apparent�contradiction�between�the�known�risk dren�living�in�the�study�areas�and�the�actual�sales�of�all�an- factors�and�the�change�in�prevalence�of�resistance�in�these�com- timicrobial�agents�in�the�study�areas�together�with�the�individual munities�be�explained?�Important�factors�such�as�the�spread�of use�of�antimicrobials�by�the�participants�was�available�for�study. novel�bacterial�clones�to�communities�with�little�or�no�herd�im- The�study�confirmed�the�risk�factors�for�carrying�PNSP�demon- munity�to�the�new�clones�has�not�been�evaluated�in�previous strated�in�the�1993�study,�i.e., antimicrobial�use,�time�from�last community-wide�studies�on�antimicrobial�resistance.�Despite antimicrobial�treatment,�age,�and�living�in�a�high�prevalence fast�means�of�transport�for�people,�the�transfer�of�new�pneu- area.�Again,�day�care�center�attendance�was�not�a�risk�factor. mococcal� clones� is� highly� time� dependent.14 International This�is�probably�because�only�17%�of�the�participants�were�not clones�are�likely�to�appear�first�in�highly�populated�urban�ar- attending�day�care�centers�and�their�siblings�and/or�friends�are eas�and�then�spread�from�there�to�rural�areas�and�distant�and therefore�highly�likely�to�be�attending�day�care�centers,�enabling smaller�urban�areas.�Reaching�remote�rural�areas�should�take efficient�transmission�from�the�day�care�centers.�The�reduced even�longer�time.�The�Spanish–Icelandic�serotype�6B�pneumo- antimicrobial�use�is�likely�to�have�contributed�to�the�reduced coccal�clone�first�appeared�in�Iceland�in�1989�and�was�almost prevalence�of�PNSP�in�areas�H�and�V�and�limited�the�increase exclusively�isolated�from�patients�living�in�the�capital�area�dur- in�areas�B�and�E. ing�the�first�2�years.�Subsequently�it�appeared�and�spread�in�the Iceland�has�a�small�homogenous�population�and�some�parts town�of�Akureyri,�which�is�the�largest�urban�area�outside�the are�sparsely�populated.�Apart�from�that,�it� is�very�similar�to capital�area�(389�km�by�road;�see�Fig.�1)�(K.G.�Kristinsson,�un- other�western�European�countries.�The�main�results�of�this�study 192 ARASON�ET�AL. demonstrating�the�fitness�of�a�particular�pneumococcal�clone�in factors�on�antimicrobial�resistance�in�pneumococci.�Microb.�Drug its�ability�to�spread�fast�in�communities�with�little�or�no�herd Resist.�3:117–123. immunity�should�therefore�also�be�applicable�to�other�countries. 9. Kristinsson,�K.G. 1999.�Modification�of�prescribers’�behavior:�the The�importance�of�such�fitness�is�obvious�if�such�clones�are Icelandic�approach.�Clin.�Microbiol.�Infect.�5(Suppl.�4):43–47. 10. Kristinsson,�K.G. 2000.�Effect�of�antimicrobial�use�and�other�risk multiresistant�and/or� virulent�and�also�for� future�vaccination factors�on�antimicrobial�resistance�in�pneumococci.�In A.�Tomasz strategies.�Interventions�can� be�effective�in� reducing�antimi- (ed.),�Streptococcus�pneumoniae: Molecular�Biology�and�Mecha- crobial�use�in�small�communities�such�as�in�Iceland,�but�they nisms�of�Disease.�Mary�Ann�Liebert�Inc.,�New�York,�pp.�419–425. may�not�lead�to�immediate�reductions�in�prevalence�of�resistant 11. Kronvall,�G. 1973.�A�rapid�slide-agglutination�method�for�typing strains.�Longitudinal�epidemiological�intervention�studies�car- pneumococci�by�means�of�a�specific�antibody�adsorbed�to�protein- ried�out�in�different�areas�and�assessing�all�known�and�likely A-containing�staphylococci.�J.�Med.�Microbiol.�6:187–190. risk�factors�are�needed�to�assist�public�health�officials�further 12. Lipsitch,�M.,�C.T.�Bergstrom,�and�B.R.�Levin. 2000.�The�epi- in�designing�the�most�effective�strategies�to�reduce�resistance demiology�of�antibiotic�resistance�in�hospitals:�paradoxes�and�pre- rates.� Future� studies� on� the� epidemiology�of� pneumococcal scriptions.�Proc.�Natl.�Acad.�Sci.�USA�97:1938–1943. clones�and�the�effects�of�interventions�must�consider�the�effect 13. Melander,�E.,�S.�Molstad,�K.�Persson,�H.B.�Hansson,�M.�Soder- strom,�and�K.� Ekdahl. 1998.�Previous�antibiotics�consumption of�distance,�time,�and�herd�immunity. and�other�risk�factors�for�carriage� of�penicillin-resistant�Strepto- coccus�pneumoniae in�children.�Eur.�J.�Clin.�Microbiol.�Infect.�Dis. 17:834–838. ACKNOWLEDGMENTS 14. Melander,�E.,�K.�Ekdahl,�H.B.�Hansson,�C.�Kamme,�M.�Lau- rell,� P.� Nilsson,� K.� Person,� M.� Soderstrom,� and�S.� Molstad. 1998.�Introduction�and�clonal�spread�of�penicillin-�and�trimetho- Special�thanks�are�due�to�all�the�children�who�participated prim/sulfamethoxazole-resistant� Streptococcus� pneumoniae, in�the�study�and�to�their�parents.�This�study�was�supported�by serotype�9V,�in�southern�Sweden.�Microb.�Drug�Resist.�4:71–78. the�Icelandic�College�of�Family�Physicians,�The�Research�Fund 15. Melander,�E.,�K.� Ekdahl,�G.�Jonsson,�and�S.�Molstad. 2000. of�the�University�of�Iceland,�and�the�Research�Fund�of�the�Land- Frequency�of�penicillin-resistant�pneumococci�in�children�is�cor- spitali�University�Hospital,�Reykjavik. related�to�community�utilization�of�antibiotics.�Pediatr.�Infect.�Dis. 19:1172–1177. 16. Molstad,�S.,�E.�Arvidsson,�I.�Eliasson,�B.�Hovelius,�C.�Kamme, and�C.�Schalen. 1992.�Production�of�betalactamase�by�respiratory REFERENCES tract�bacteria�in�children:�relationship�to�antibiotic�use.�Scand.�J. Prim.�Health.�Care.�10:16–20. 1. Arason,�V.A.,�K.G.�Kristinsson,�J.A.�Sigurdsson,�G.�Stefans- 17. Seppala,�H.,�T.�Klaukka,�J.�Vuopio-Varkila,�A.�Muotiala,�H. dottir,�S.�Molstad,�and�S.�Gudmundsson. 1996.�Do�antimicro- Helenius,�K.�Lager,�and�P.�Huovinen. 1997.�The�effect�of�changes bials�increase�the�carriage�rate�of�penicillin�resistant�pneumococci in�the�consumption�of�macrolide�antibiotics�on�erythromycin�re- in�children?�Cross�sectional�prevalence�study.�Br.�Med.�J.�313:387– sistance� in� group� A� streptococci� in� Finland.� N.� Engl.� J.� Med. 391. 337:441–446. 2. Austin,�D.J.,�K.G.�Kristinsson,�and�R.M.�Anderson. 1999.�The 18. Soares,� S.,� K.G.� Kristinsson,� J.M.� Musser,� and� A.� Tomasz. relationship�between�the�volume�of�antimicrobial�consumption�in 1993.�Evidence�for� the� introduction�of�a� multiresistant�clone� of human�communities�and�the�frequency�of�resistance.� Proc.�Natl. serotype�6B�Streptococcus�pneumoniae from�Spain�to�Iceland�in Acad.�Sci.�USA�96:1152–1156. the�late�1980s.�J.�Infect.�Dis.�168:158–163. 3. Ekdahl,� K.,� H.B.� Hansson,� S.� Molstad,� M.� Soderstrom,� M. 19. Swenson,�J.M.,�B.C.�Hill,�and�C.�Thornsberry. 1986.�Screening Walder,�and�K.�Persson. 1998.�Limiting�the�spread�of�penicillin- pneumococci� for� penicillin� resistance.� J.� Clin.� Microbiol. resistant� Streptococcus�pneumoniae: experiences�from�the�South 24:749–752. Swedish�Pneumococcal�Intervention�Project.�Microb.�Drug�Resist. 20. Vilhelmsson,�S.E.,�A.�Tomasz,�and�K.G.�Kristinsson. 2000.�Mo- 4:99–105. lecular�evolution�in�a�multidrug-resistant�lineage�of�Streptococcus 4. Guillemot,�D.,�C.�Carbon,�B.�Balkau,�P.�Geslin,�H.�Lecoeur,�F. pneumoniae: emergence�of�of�strains�belonging�to�the�serotype�6B Vauzelle-Kervroëdan,� G.� Bouvenot,� and� E.� Eschwége. 1998. Icelandic�clone�that�lost�antibiotic�resistance�traits.�J.�Clin.�Micro- Low�dosage�and�long�treatment�duration�of�beta-lactam:�risk�fac- biol.�38:1375–1381. tors�for�carriage�of�penicillin-resistant�Streptococcus�pneumoniae. 21. World� Health� Organisation.� 1992.� Anatomical� Therapeutical J.�Am.�Med.�Assn.�279:365–370. Chemical�(ACT)�classification�index�including�defined�daily�doses 5. Jorgensen,�J.J.,�J.D.�Turnidge,�and�J.A.�Washington. 1999.�An- (DDDs)�for�plain�substances.�Oslo:�WHO�Collaborating�Centre�for timicrobial�susceptibility�tests:�dilution�and�disk�diffusion�meth- Drug�Statistics�Methodology. ods.�In P.R.�Murray,�E.J.�Baron,�M.A.�Pfaller,�F.C.�Tenover,�and th R.H.�Yolken�(eds.),�Manual�of�clinical�microbiology,�7 ed.�Amer- Address�reprint�requests�to: ican�Society�for�Microbiology.�ASM�Press,�Washington,�D.C.,�pp. Dr.�Karl�G.�Kristinsson 1526–1543. Department�of�Microbiology 6. Kristinsson,�K.G.,�M.A.�Hjalmarsdottir,�and�O.�Steingrimsson. Landspitali�University�Hospital 1992.�Increasing�penicillin�resistance�in�pneumococci�in�Iceland. Lancet.�339:1606–1607. P.O.�Box�1465 7. Kristinsson,�K.G. 1995.�Epidemiology�of�penicillin�resistant�pneu- 121�Reykjavik,�Iceland mococci�in�Iceland.�Microb.�Drug�Resist.�1:121–125. 8. Kristinsson,�K.G. 1997.�Effect�of�antimicrobial�use�and�other�risk E-mail: [email protected] 109

PAPER III

Tympanostomy tube placements, sociodemographic factors and parental expectations for management of acute otitis media in Iceland

VILHJALMUR A. ARASON, MD, JOHANN A. SIGURDSSON, MD, PHD, KARL G. KRISTINSSON, MD, PHD AND SIGURDUR GUDMUNDSSON, MD, PHD

Background. Widespread antimicrobial use is a ing the preceding 8 weeks at last once for AOM risk factor for development of antimicrobial re- compared with 14% of those without tubes (P � sistance. Antimicrobial treatment of acute otitis 0.97). Parents in the area where antimicrobial media (AOM) may not always be necessary. Little consumption was lowest were less likely to ac- is known about the influence of parental expec- cept antimicrobial treatment than parents in the tations on physicians’ decision-making in rela- other areas (P � 0.005). Parents of children who tion to treatment of AOM. Evidence is insuffi- had previously received antimicrobials for AOM cient as to whether tympanostomy tube were more likely to accept antimicrobials (P � placement reduces antibiotic consumption. 0.04). Methods. We randomly selected 1030 children 1 Conclusions. Parental expectations to antimi- to 6 years old living in 4 geographic areas in crobial treatment and awareness about resis- Iceland to be invited to participate in the study. tance development appear to influence treat- Information about sociodemographic factors, an- ment strategies for AOM. The high rate of timicrobial prescriptions and their indications tympanostomy tube placement in preschool chil- during the preceding 12 months, tympanostomy dren does not result in reduced antimicrobial tube placements and parental views on antimi- consumption. crobial use and bacterial resistance were obtained from a questionnaire completed by the parents and medical records. INTRODUCTION Results. The incidence of AOM episodes result- Antimicrobial overuse is one of the major causes for ing in antimicrobial prescription for 804 children the development of antimicrobial resistance among 1 recruited into the study was 0.7 (95% confidence common pathogens. A strong association between the interval, 0.6 to 0.8) per child per year, highest overall antimicrobial use and carriage of penicillin- among children age 1 year, i.e. 1.8 prescriptions resistant pneumococci has been documented in Icelan- 2 (95% confidence interval, 1.4 to 2.2). The cumula- dic children. During the years 1993 to 1998 an Icelan- tive incidence of tympanostomy tube placements dic public information campaign accompanied by was �30%. Antimicrobial use during the preced- targeted information to physicians resulted in a 30% ing 8 weeks for children with and without tubes reduction of the total antimicrobial prescriptions rate 3 did not differ (P � 0.36). Fifteen percent of chil- for acute otitis media (AOM) in children. A reduced dren with tubes had received antimicrobials dur- prevalence of penicillin resistance among pneumococci followed in the wake of the campaign.4 AOM was the single most common (65%) diagnosis resulting in antimicrobial prescription for Icelandic Accepted for publication July 25, 2002. 2 From the Department of Family Medicine, University of Ice- children in 1993 which is in agreement with studies land, Solvangur, Hafnarfjordur (VAA, JAS), and the Department from other countries.5, 6 Previously we demonstrated of Clinical Microbiology, Landspitali University Hospital (KGK) an association between antimicrobial consumption and and Directorate of Public Health (SG), Reykjavik, Iceland. Key words: Acute otitis media, antimicrobial use, drug pre- prevalence of penicillin-nonsusceptible pneumococci in scription, tympanostomy tube, parental expectations, Iceland. relation to AOM.3 There are several randomized clini- Address for reprints: Vilhja´lmur Ari Arason, M.D., Depart- cal trials7, 8 and metaanalyses9, 10 that indicate that ment of Family Medicine, Solvangur Health Centre, Solvangs- vegur 3, 220 Hafnarfjordur, Iceland. Fax (354) 55026 71; E-mail antimicrobial treatment of AOM may not always be [email protected]. necessary or that treatment may have only a limited DOI: 10.1097/01.inf.0000040702.00373.95 effect. Despite successful efforts to reduce antibiotic 1110 Vol. 21, No. 12, Dec. 2002 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL 1111 consumption in Iceland, there could be a potential for date of the last antimicrobial prescription was noted, further reduction of antibiotic prescriptions for AOM. together with the type of agent prescribed and the Physicians considering an antimicrobial prescription clinical indication (diagnosis) for the prescription. Past may consider not only clinical symptoms and signs but or present use of tympanostomy tubes was recorded. also social factors and parental expectations.11–14 The The information collected from parents was matched aim of this study was to investigate factors contribut- with information available from the medical records at ing to antibiotic prescriptions for AOM in preschool the local health center. children, including sociodemographic factors, parental Parents were also asked to complete a questionnaire expectations and awareness to resistance development, about their personal preferences in relation to antimi- as well as the impact of former antimicrobial usage by crobial treatment in the case of (1) unspecified upper the index child. We also evaluated whether tympanos- respiratory infections (common cold) and (2) acute tomy tubes placement reduces antibiotic consumption otitis media. Parents answered the question whether it among children. was always, sometimes or never appropriate to give antimicrobials in these two situations, or whether they METHODS did not know. They were then asked to agree, disagree Study population and design. Children in four or give no comment (or answer “do not know”) to the geographic areas in Iceland were included in the study following two statements: “Some pathogens are becom- (Fig. 1). At the end of 1997 these areas had a total ing resistant to antimicrobials” and “Inappropriate population of 27 013 inhabitants, of whom 2900 were antimicrobial use can lead to antimicrobial resistance children from 1 to 6 years old, according to the National problems among common pathogens.” Registry. These areas were served by 17 general prac- The study was approved by the National Bioethics titioners. The areas were: Hafnarfjordur (H), 18 203 Committee and the National Data Protection Commis- inhabitants, including 1989 children 1 to 6 years old; sion, Iceland. Vestmannaeyjar (V) with 4640 inhabitants, including Statistical analysis. The Pearson chi square test 512 children; Egilsstadir (E), with 3076 inhabitants, was used for univariate analysis of categorical vari- including 300 children; and Bolungarvik (B), with 1094 ables. Multivariate logistic regression was used to inhabitants and 99 children. After computer random- estimate the odds if a child had been given treatment ization of all 2900 eligible children, 1030 children (36% by antimicrobials because of AOM or not, adjusted to of the total) were selected, and their parents received a age, gender, residence, having siblings or not and letter inviting them to participate in the study together day-care attendance to control interdependence. The with their child (H, 20%; V, 58%; E, 63%; and B, 62%). multivariate logistic regression was also used to deter- Informed parental consent was obtained from all par- mine the odds if a child had received tympanostomy ticipants. tubes or not, adjusted for residence and gender and for Data were collected in April and May 1998. Parents the odds if a child had received antimicrobials during of participating children received postal question- the preceding 8 weeks or not, adjusted for age, and if naires, addressing sociodemographic factors, number the child had tympanostomy tube inserted or not. of children in the household and day-care attendance. Furthermore the logistic regression method was used Antimicrobial use was measured as the number of oral for the odds that a parent would express the opinion antimicrobial courses during the preceding year. The that it is never appropriate to give antimicrobial treatment for colds (unspecified upper respiratory tract infection) rather than sometimes, adjusted for residence, the child having siblings or not, parental view that AOM should be treated with antimicrobials or not and whether a child had received antimicrobial treatment for otitis media during the last 12 months or not. Individual regression coefficients were tested with the Wald statistic, and 95% confidence intervals (95% CI) were calculated for the odds. The statistical analyses were performed with the SPSS program for Windows (Advanced Statistics Release 8.0; SPSS Inc, Chicago, Ill.). The level of statistical significance was taken as 0.05.

RESULTS Eight hundred four children and their parents par- FIG. 1. The study areas in Iceland. ticipated in the study. The mother was the responder in 1112 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL Vol. 21, No. 12, Dec. 2002

TABLE 1. Study population

Mean Age of Area Participants Boys Girls Participants

Hafnarfjordur 331 (75)* 173 (52.3) 158 (47.7) 4.07 � 1.75† Vestmannaeyjar 244 (76) 131 (53.7) 113 (46.3) 4.20 � 1.67 Egilsstadir 174 (88) 83 (47.7) 91 (52.3) 4.04 � 1.78 Bolungarvik 55 (83) 28 (50.9) 27 (49.1) 4.23 � 1.72

Total 804 (78) 415 (51.6) 389 (48.4) 4.11 � 1.73 * Numbers in parentheses, percent enrolled of those invited. † Mean � SD.

92% of cases. This represented a response rate ranging tympanostomy tube usage was obtained for 735 chil- from 75 to 88% of the total random sample of the study dren. Among these 213 or 29% (95% CI 26 to 33%) had areas (Table 1). A total of 439 (54.6%) had received at some point received tympanostomy tube in one or antimicrobial treatment at least once during the pre- both ears. Twenty-three percent (95% CI 16 to 31%) of ceding 12 months. The total incidence of antibiotic 1-year-old children had already received tubes (Fig. 2). treatments for any reason was 1.21 per child per year The percentage of children who had received tubes was (95% CI 1.09 to 1.32). This number was significantly 26% in Areas E and H, 34% in Area B and 35% in Area higher in area V, 1.51 (95% CI 1.26 to 1.75) than in area V(P � 0.113). Adjusted for area of residence, the odds E, 0.89 (95% CI 0.60 to 1.09). In area H the incidence for boys to receive tympanostomy tubes (128 of 377) was 1.16 (95% CI 0.99 to 1.33), and in area B it was was 1.56 as compared with girls (88 of 358) (P � 0.01). 1.15 (95% CI 0.72 to 1.57). Of 88 children currently having tympanostomy tubes, Antimicrobial prescriptions for acute otitis 31 (35%) had received oral antimicrobials at least once media. The yearly incidence of disease episodes diag- during the previous 8 weeks compared with 162 of 645 nosed as AOM and resulting in oral antimicrobial children (25%) not having tympanostomy tubes (P � treatment was 0.70 (95% CI 0.61 to 0.79) per child, 0.059). When adjusted also for age the odds if child constituting 58% of total antimicrobial prescriptions received antimicrobials or not was not statistically for any reason. The rate was highest, 1.79 (95% CI 1.40 significant (P � 0.36). to 2.18) per child, among children 1 year of age and Thirteen children with tympanostomy tubes (15%) lowest among the 6-year-olds, i.e. 0.25 (95% CI 0.15 to had received oral antimicrobials for AOM during the 0.36) per child. Analyzed by areas the incidence was: E, preceding 8 weeks (mean, 3.77 weeks; 95% CI 2.11 to 0.57 (95% CI 0.41 to 0.74); B, 0.65 (95% CI 0.32 to 0.99); 5.43), compared with 90 children (14%) without tubes H, 0.69 (95% CI 0.56 to 0.83); and V, 0.81 (95% CI 0.62 (mean, 3.76 weeks; 95% CI 3.24 to 4.27) (P � 0.97). to 1.00). Parental expectations and awareness in rela- The types of antimicrobial agent used in the most tion to antimicrobial treatment. Parents in Area E, recent treatment for AOM were amoxicillin or ampicillin in 111 cases (50.7%), amoxicillin plus clavulanic acid in 56 cases (25.6%), trimethoprim-sulfamethox- TABLE 2. Adjusted odds ratio for children who have been treated with antimicrobials for acute otitis media in the azole in 35 cases (16.0%), penicillin in 11 cases (5,0%), preceding 12 months (N � 277) as opposed to not (N � 519) erythromycin in 1 case (0.5%) and other classes (or not by multivariate analysis (796 cases analyzed, data missing known) in 5 cases (2.3%). in 8 cases) The yearly incidence of clinical episodes other than Odds Variable No. 95% CI P* AOM resulting in antimicrobial prescriptions were: Ratio tonsillitis, 0.18 (95% CI 0.15 to 0.21); acute sinusitis, Age 0.10 (95% CI 0.08 to 0.13); bronchitis, 0.07 (95% CI 0.05 1–3 yr 386 1 4–6 yr 410 0.24 0.17–0.33 0.0001 to 0.09); pneumonia, 0.07 (95% CI 0.05 to 0.09); skin Gender infections, 0.05 (95% CI 0.04 to 0.07); and urinary tract Male 409 1 Female 387 1.25 0.92–1.71 0.156 infections, 0.04 (95% CI 0.02 to 0.06). Siblings Sociodemographic risk factors for antimicro- No 128 1 Yes 668 1.04 0.69–1.58 0.844 bial prescription for acute otitis media. Young age Residence 0.558 (1 to 3 years old) was significantly associated with more Area H 327 1 Area V 242 1.21 0.83–1.74 0.332 antimicrobial prescriptions for AOM than in children Area E 172 0.89 0.59–1.35 0.581 ages 4 to 6 years old (Table 2). Gender, number of Area B 55 1.16 0.62–2.17 0.636 Day care siblings, residence and day-care attendance did not No 145 1 influence the odds of receiving antimicrobials for AOM. Yes 651 1.01 0.68–1.50 0.972 Use of tympanostomy tubes. Information about * Overall significance: chi square, 88.8; df, 7; P � 0.0001. Vol. 21, No. 12, Dec. 2002 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL 1113 ceived antibiotics for AOM. Tympanostomy tube usage for their child did not influence parental opinion in relation to this matter.

DISCUSSION AOM is the most common clinical diagnosis underlying antimicrobial prescriptions for Icelandic pre- school children. Physician treatment strategies for this condition are likely to have a significant impact on the total antibiotic consumption in the community. The study indicates that antimicrobial consumption in a community can be influenced by efforts that aim at increasing parental interest and awareness in relation to antibiotic use. As has been shown in a recent study,15 involving patients more actively in evaluating the need for antimicrobial treatment in situations in

FIG. 2. Cumulative prevalence in percentage (� 95% CI) of which convincing evidence for a clear benefit is lacking, preschool children in Iceland who have received tympanostomy may lead to reduced drug consumption. tube placements. Parents of children who had previously been treated for AOM with antimicrobials were more likely to con- where antibiotic consumption was lowest, answered cur with antimicrobial therapy, even for the common significantly more often than parents in other areas cold. This may be caused by positive reinforcement that it was never appropriate to give antimicrobial given that the child might have improved from upper treatment for unspecified upper respiratory tract infec- airway infections on a previous occasion while taking tion (Table 3). The statement “some pathogenic bacte- an antimicrobial agent. Similar findings have been ria are becoming resistant to antimicrobials” was an- reported for treatment of sore throat.16 swered by 798 parents, of whom 719 agreed (89.4%), 2 A major benefit of this study is the comparison (0.2%) disagreed, 33 (4.1%) were passive and 44 (5.5%) between geographically well-defined areas. The impact did not know. Similarly 797 parents gave their opinion of day-care attendance is hard to evaluate on the basis on the statement “inappropriate antimicrobial use can of this study, given that �80% of 1- to 6-year-old lead to resistance development among common patho- children in Iceland attend day care. Other studies gens” and 644 (80.1%) agreed, 4 (0.5%) disagreed, 76 have, however, demonstrated that day care appears to (9.5%) were passive and 73 (9.1%) did not know. The have a clear impact on the number of treatment cours- response from parents to the questionnaire addressing es.17 issues of parental expectations and awareness further There was a surprisingly high use of tympanostomy indicated that parents who consider it inappropriate to tubes among the participating children. This number is treat unspecified upper respiratory tract infections much higher than in the south of Sweden where �10% with antimicrobials significantly more often preferred of children had a history of tympanostomy tube inser- that AOM not be treated with antibiotics (Table 4). tions.18 Use appears to be even less in the United They also more often considered it appropriate to States where a recent study found that 1.8% of 1-year- prescribe antimicrobials for unspecific upper respira- old children and 4.2% of 2-year-old children had tym- tory tract infection if their child had previously re- panostomy tube placement.19 The explanation for these

TABLE 3. Results from parent’s questionnaire about appropriate antimicrobial usage for upper respiratory tract infections for children

Question 2†: Is It Appropriate to Give Antimicrobial Question 1*: Is It Appropriate to Give Antimicrobial Treatment for Unspecified Upper Respiratory Tract Infection Treatment for AOM? (Common Cold)?

Always Sometimes Never Don’t know Always Sometimes Never Don’t know

Area H 27 (8.3)‡ 286 (87.5) 3 (0.9) 11 (3.4) 0 (0.0) 154 (47.2) 148 (45.4) 24 (7.4) Area V 28 (11.5) 197 (81.1) 4 (1.6) 14 (5.8) 1 (0.4) 121 (49.8) 95 (39.1) 26 (10.7) Area E 9 (5.2) 152 (87.9) 5 (2.9) 7 (4.0) 0 (0.0) 50 (28.9) 109 (63.0) 14 (8.1) Area B 2 (3.6) 51 (92.7) 1 (1.8) 1 (1.8) 0 (0.0) 21 (38.2) 25 (45.5) 9 (16.4)

Total 66 (8.3) 686 (86.0) 13 (1.6) 33 (4.1) 1 (0.1) 346 (43.4) 377 (47.3) 73 (9.2) * Pearson chi square, 13.01; df 9; P � 0.159. † Pearson chi square, 32.27; df 9; P � 0.0001. ‡ Numbers in parentheses, percent. 1114 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL Vol. 21, No. 12, Dec. 2002

TABLE 4. Adjusted odds ratio for parental answers from the questionnaire; “Is it appropriate to give antimicrobial treatment for unspecified upper respiratory tract infection (cold), never as opposed to sometimes

Variable No. Odds Ratio 95% CI P*

Residence 0.005 Area E 124 1 Area H 277 0.50 0.32–0.78 0.002 Area V 190 0.45 0.28–0.72 0.001 Area B 39 0.68 0.32–1.43 0.302 Siblings No 104 1 Yes 526 1.10 0.72–1.71 0.652 Day care No 119 1 Yes 511 1.08 0.71–1.63 0.728 Want to treat acute otitis media with antibiotics? Always 58 1 Sometimes 572 4.49 2.30–8.74 0.00001 Antibiotic treatment for AOM last 12 mo? No 407 1 Yes 223 0.70 0.50–0.98 0.040 Tympanostomy tube now or before? No 442 1 Yes 188 0.94 0.66–1.35 0.732 * Chi square, 43.812; df 8; overall significance, P � 0.00001. differences is not clear. Availability of physicians did carriage rate of penicillin resistant pneumococci in children? not appear to influence treatment strategies in general, Cross sectional prevalence study. BMJ 1996;313:387–91. 3. Arason VA, Gunnlaugsson A, Sigurdsson JA, Erlendsdottir including selection of children for tympanostomy tube H, Gudmundsson S, Kristinsson KG. Clonal spread of resis- placements. The numbers of ear, nose and throat tant pneumococci despite diminished antimicrobial use. Mi- physicians and general practitioners in Iceland were crob Drug Resist 2002;8:187–92. 4. Kristinsson KG. Modification of prescribers’ behavior: the 7.3 and 56.7/100 000 inhabitants, respectively, which is Icelandic approach. Clin Microbiol Infect 1999;5(Suppl 4): comparable with conditions in Sweden, where the cor- 43–7. responding figures have been 6.6 and 59.1/100 000.20 5. McCaig LF, Hughes JM. Trends in antimicrobial drug prescribing among office-based physicians in the United States. The main indications for tympanostomy tube place- JAMA 1995;273:214–9. ments are persistent fluid in the middle ear and recur- 6. Froom J, Culpepper L, Jacobs M, et al. Antimicrobials for rent AOM. This study focuses on causes of antimicro- acute otitis media? A review from the International Primary Care Network. BMJ 1997;315:98–102. bial treatment in children, especially the diagnosis of 7. Little P, Gould C, Williamson I, Moore M, Warner G, Dun- AOM, with and without tympanostomy tubes. It did leavey J. Pragmatic randomised controlled trial of two pre- not specifically address the criteria for insertion of scribing strategies for childhood acute otitis media. BMJ 2001;322:336–42. tympanostomy tubes, but we assume that the indica- 8. Damoiseaux R, Van Balen F, Hoes A, Verheij T, De Melker R. tions are comparable with those in the US, Canada and Primary care based randomised double blind trial of amoxi- Scandinavia, given that all ear, nose and throat spe- cillin versus placebo for acute otitis media in children aged under 2 years. BMJ 2000;320:350–4. cialists in Iceland and most of remitting general prac- 9. Rosenfeld RM, Vertrees JE, Carr J et al. Clinical efficacy of titioners have completed their postgraduate training antimicrobial drugs for acute otitis media: metaanalysis of abroad, usually in the above-mentioned countries. 5400 children from thirty-three randomized trials. J Pediatr 1994;124:355–67. Tympanostomy tube placement was not associated 10. Del Mar C, Glasziou P, Hayem M. Are antibiotics indicated as with reduced antimicrobial use for AOM in the present initial treatment for children with acute otitis media? A study. This does not exclude the possibility that a metaanalysis. BMJ 1997;314:1526–9. subgroup of infection-prone children with chronic mid- 11. Howie JG. Some non-bacteriological determinants and implications of antibiotic use in upper respiratory tract illness. dle ear effusion might benefit from the placement of Scand J Infect Dis 1983;39(Suppl):68–72. tympanostomy tubes. 12. Macfarlane J, Holmes W, Macfarlane R, Britten N. Influence of patients’ expectations on antibiotics management of acute ACKNOWLEDGMENTS lower respiratory illness in general practice: questionnaire study. BMJ 1997;315:1211–14. We thank the children and parents who participated in the 13. Butler C, Rollnick S, Pill R, Maggs-Rapport F, Stott N. study and the general practitioners who assisted in recruiting the Understanding the culture of prescribing: qualitative study of participants. This study was supported by the Icelandic College of general practitioners’ and patients’ perceptions of antibiotics Family Physicians and The Research Fund of the University of for sore throat. BMJ 1998;317:637–42. Iceland, Reykjavik. 14. Hamm RM, Hicks RJ, Bemben DA. Antibiotics and respiratory infections: are patients more satisfied when expectations REFERENCES are met? J Fam Pract 1996;43:56–62. 1. Levy SB. Multidrug resistance: a sign of the times. N Engl 15. Macfarlane J, Holmes W, Gard P, Thornhill D, Macfarlane R, J Med 1998;338:1376–8. Hubbard R. Reducing antibiotic use for acute bronchitis in 2. Arason VA, Kristinsson KG, Sigurdsson JA, Stefansdottir G, primary care: blinded, randomised controlled trial of patient Mo¨lstad S, Gudmundsson S. Do antimicrobials increase the information leaflet. BMJ 2002;324:91–4. Vol. 21, No. 12, Dec. 2002 THE PEDIATRIC INFECTIOUS DISEASE JOURNAL 1115

16. Little PS, Gould C, Williamson I, Warner G, Gantley M, M, Ekdahl K. Previous antibiotics consumption and other Kinmonth AL. Reattendance and complications in a random- risk factors for carriage of penicillin-resistant Streptococcus ised trial of prescribing strategies for sore throat: the medi- pneumoniae in children. Eur J Clin Microbiol Infect Dis calising effect of prescribing antibiotics. BMJ 1997;315: 1998;17:834–8. 350–2. 19. Paradise JL, Rockette HE, Colborn DK et al. Otitis media in 17. Uhari M, Ma¨ntysaarik K, Niemela¨ M. A meta-analytical 2253 Pittsburgh-area infants: prevalence and risk factors review of the risk factors for acute otitis media. Clin Infect during the first two years of life. Pediatrics 1997;99:318–33. Dis 1996;22:1079–83. 20. Medical Association in the Nordic countries 1999. Available 18. Melander E, Mo¨lstad S, Persson K, Hansson HB, So¨derstro¨m at: http://www.slf.se. Accessed October 22, 2002.

Population-based surveillance for hospitalized and ambulatory pediatric invasive pneumococcal disease in Santiago, Chile

ROSANNA LAGOS, MD, ALMA MUN˜ OZ, MD, MARI´A TERESA VALENZUELA, MD, INGRID HEITMANN, MD AND MYRON M. LEVINE, MD, DTPH

Background. Nine- and 11-valent pneumococ- with high fever seen in the ER as standard prac- cal conjugate vaccines under development may tice. Streptococcus pneumoniae isolates were se- control pediatric pneumococcal disease in non- rotyped. industrialized countries. Because these vaccines Results. Blood cultures of 18 (1.2%) of 1503 are expensive, population-based surveillance of outpatients 6 to 35 months of age with high fever pneumococcal disease in children <36 months of in the pilot study yielded S. pneumoniae. In the age was undertaken in Santiago, Chile to provide ensuing 24 months 236 children <36 months old health authorities with reliable data on the bur- were hospitalized with invasive pneumococcal den of invasive pneumococcal disease and caus- disease (incidence, 33.9 cases/105 children), and ative serotypes, including those in outpatients 188 bacteremias were detected among ambula- with high fever. tory ER patients with high fever (incidence, 27.0 Methods. Automated blood culture machines cases/105 children). Although serotypes were were introduced into 9 hospitals that admit 85% similar among hospitalized and ambulatory of all hospitalized children in Santiago. Acutely cases (except 18C, which was more common in ill pediatric febrile ambulatory patients are at- the latter), case fatality was 9.5% in hospitalized tended at 8 emergency rooms (ERs) and 36 ur- (21 of 236) vs. 0% in ambulatory cases (0 of 188) gent primary care services. After a 12-month (P � <0.0001). High level resistance to penicillin pilot study in 3 ERs, health authorities collected (25.8% vs. 10.1%) and cefotaxime (19.5% vs. 6.2%) blood cultures from children <36 months of age was observed more often among pneumococcal isolates from hospitalized than among ambula- Accepted for publication Aug. 29, 2002. tory cases (P < 0.001). From Centro para Vacunas en Desarrollo (RL, AM, MTV), Conclusions. ER surveillance detected approx- Hospital de Nin˜ os, Roberto del Rio (RL) and Instituto de Salud Pu´ blica de Chile (MTV, IH), Santiago, Chile; and Center for imately one case of pneumococcal bacteremia Vaccine Development, University of Maryland School of Medi- among febrile ambulatory patients for each hos- cine, Baltimore, MD (RL, MML). Key words: Pneumococcus, Streptococcus pneumoniae, conju- pitalized invasive case. Because 71% of cases gate vaccines, immunization, epidemiology. were caused by vaccine serotypes (and 87% by Address for reprints: Rosanna Lagos, M.D., Centro para Vacu- vaccine serogroups), 9- and 11-valent pneumo- nas en Desarrollo, Hospital Roberto del Rio, Avenida Professor Zan˜ artu 1085, Santiago, Chile. Fax (56)(2) 735-7263; E-mail coccal conjugate vaccines could prevent most [email protected]. invasive pediatric pneumococcal disease in DOI: 10.1097/01.inf.0000040703.99011.5c Chile. 117

PAPER IV

Scandinavian Journal of Primary Health Care, 2005; 23: 184�/191

ORIGINAL ARTICLE

Otitis media, tympanostomy tube placement, and use of antibiotics

Cross-sectional community study repeated after five years

VILHJALMUR A. ARASON1, JOHANN A. SIGURDSSON1, KARL G. KRISTINSSON2, LINN GETZ1 & SIGURDUR GUDMUNDSSON3

1Department of Family Medicine, University of Iceland, Solvangur, Hafnarfjordur, 2Department of Clinical Microbiology, Landspitali University Hospital, Reykjavik, 3Directorate of Public Health, Reykjavik, Iceland

Abstract Objective. To investigate potential links between antimicrobial drug use for acute otitis media (AOM) and tympanostomy tube placements, and the relationship between parental views and physician antimicrobial prescribing habits. Design. Cross- sectional community study repeated after five years. Subjects. Representative samples of children aged 1�/6 years in four well- defined communities in Iceland, examined in 2003 (n�/889) and 1998 (n�/804). Main outcome measures. Prevalence of antimicrobial treatments for AOM, tympanostomy tube placements, and parental expectations of antimicrobial treatment. Results. Tympanostomy tubes had been placed at some time in 34% of children in 2003, as compared with 30% in 1998. A statistically significant association was found between tympanostomy tube placement rate and antimicrobial use for AOM in 2003. In the area where antimicrobial use for AOM was lowest in 1998, drug use had further diminished significantly. At the same time, the prevalence of tympanostomy tube placements had diminished from 26% to 17%. Tube placements had increased significantly, from 35% to 44%, in the area where antimicrobial use for AOM was highest. Parents in the area where antimicrobial consumption was lowest and narrow spectrum antimicrobials were most often used were less likely to be in favour of antimicrobial treatment. Conclusions. Comparison between communities showed a positive correlation between antimicrobial use for AOM and tympanostomy tube placements. The study supports a restrictive policy in relation to prescriptions of antibiotics for AOM. It also indicates that well-informed parents predict a restrictive prescription policy.

Key Words: Acute otitis media, antimicrobial use, drug prescription, epidemiology, Iceland, intervention, parental expectations, tympanostomy tube placement

Acute otitis media (AOM) is the single most In Iceland, 30% of pre-school children have had common diagnosis resulting in antimicrobial pre- tympanostomy tube placements for recurrent or scription for children in the Western world [1�/4], chronic otitis media. It is unclear whether this is including Iceland. Nevertheless antimicrobial treat- due to high disease prevalence or medical over ment of AOM is debatable. Several randomized treatment. clinical trials [5,6] and meta-analyses [7,8] indicate that it may often be unnecessary, yet severe infec- . We found a positive correlation between tions such as acute mastoiditis can complicate tympanostomy tube placements and rate of AOM. Comparison of the incidence of mastoiditis antimicrobial drug prescription for acute in the USA where AOM has usually been treated otitis media. with antimicrobials and the Netherlands where . In regions with diminishing use of antimi- AOM is usually not treated with antimicrobials, crobials, a decrease in tympanostomy place- however, reveals a negligible difference [9]. A ments could be observed over time. restrictive antibiotic policy for AOM therefore

Correspondence: Vilhjalmur Ari Arason MD, Department of Family Medicine, Solvangur Health Center Solvangsvegur 3, IS-220 Hafnarfjordur, Iceland. E-mail: [email protected]

(Received 30 December 2004; accepted 19 April 2005) ISSN 0281-3432 print/ISSN 1502-7724 online # 2005 Taylor & Francis DOI: 10.1080/02813430510031298 Association between antibiotic usage for AOM and tympanostomy tube placement 185

. Parental knowledge about appropriate use of access to such specialists in Reykjavik. Informed antimicrobial drugs was found to be related parental consent was obtained for all participants. to physician prescribing habits. The parents received a questionnaire regarding sociodemographic factors, number of children and appears justifiable. Such a policy is further sup- smoking habits in the household, and day care ported by the documented link between high con- attendance. Antimicrobial use was measured as the sumption of antimicrobials and development of number of oral antimicrobial courses during the antimicrobial resistance among common pathogens preceding year, according to parents’ recollection. [1,10,11]. A strong association between antimicro- The date of the last antimicrobial prescription was bial use for AOM and carriage of penicillin non- noted, together with the type of agent prescribed and susceptible pneumococci in children has been the clinical indication (diagnosis) for the prescrip- demonstrated [12]. Further knowledge about the tion. A history of past or present use of tympanost- short- and long-term impact of different treatment omy tubes was recorded. Information gathered from strategies for otitis media is important. parents was matched with information from the Tympanostomy tube placement is a well estab- medical records at the local health centre. Parents lished treatment option for chronic effusion in the were furthermore asked to complete a questionnaire middle ear and recurrent episodes of AOM [13], yet about their personal views in relation to antimicro- the consequences of this intervention are not clear bial treatment, similar to the 1998 study [2]. The

[14�/16]. The cumulative prevalence of tympanost- study was approved by the National Bioethics omy tube placement among Icelandic pre-school Committee and the National Data Protection Com- children has been shown to be 30% [2], which is mission, Iceland. much higher than reported in other countries [17]. Furthermore, children with tympanostomy tubes received as many antimicrobial courses as children Statistical analysis without tubes. The statistical methods have been described in detail The aim of the present study was to investigate elsewhere [2]. Fisher’s exact test and the Pearson potential links between antimicrobial treatment for chi-square test were used for univariate analysis of AOM and tympanostomy tube placements and categorical variables. Linear regression analysis was evaluate the impact of sociodemographic factors used to estimate correlation coefficient (r) and 95% and parental views on physician prescribing habits. confidence interval for the slope of mean number of We approached these research questions by con- antimicrobial courses for AOM compared with ducting a cross-sectional investigation in four well- tympanostomy tube placement rate by areas and defined areas with a five-year interval. mean number of total antimicrobial courses compared with the prevalence of parents finding it Material and methods appropriate sometimes to treat common cold with antimicrobials. Multivariate logistic regression mod- Study population and design els were used to estimate odds ratio. Individual Eligible participants included all children 1 to 6 regression coefficients were tested with the Wald years of age living in the four Icelandic communities statistic and 95% confidence intervals were calcu- Hafnarfjo¨rdur (H), Vestmannaeyjar (V), Egilsstadir lated for the odds. The statistical analyses were (E), and Bolungarvik (B). All eligible children in V, performed with the SPSS† program for Windows E, and B were invited to participate, whilst a random (Advanced Statistics Release 8.0, SPSS Inc, sample was invited in area H (Table I). The study Chicago, Ill.). The level of statistical significance areas were served by a total of 19 general practi- was taken as 0.05. tioners (GPs) (18.2 positions), of whom 11 were the same individuals as in the 1998 study. The organiza- tional structure of the healthcare service was similar Results for both study periods, except in area H which is a Participation suburb of Reykjavik. Emergency appointments were more often provided by doctors outside area H in In total, 889 children participated (see Table I), 2003 than in 1998, resulting in somewhat declining representing a response rate from 76 to 84 percent. continuity of care in area H. The same ear, nose, and According to the questionnaires most of the children throat specialists were responsible for bi-monthly attended day care centres (84�/94%). The child’s visits to each of the areas V, E, and B during the mother provided the parental information in 90% of years 1998 and 2003. Inhabitants in area H had easy cases. 186 V. A. Arason et al.

Prescription of antibiotics A total of 48% of the participating children had received oral antimicrobial treatment at least once SD) / 1.75 1.65 1.67 1.57 1.78 1.71 1.72 1.64 1.73 1.64 / / / / / / / / / / 9 9 9 9 9 9 9 9 9 9 9 during the preceding 12 months, compared with

55% in 1998 (p�/0.007). The mean number of 3.89 4.11 4.23 4.16 4.22 4.20 4.04 4.07 4.37 4.20 (years antibiotic treatments per year was 1.06 (1.21 in 1998, Table II). The usage was significantly higher Mean age of participants in area V compared with the other areas on both occasions. The proportion of antimicrobial prescriptions for AOM was about the same (57%) as in 1998 rate 83% 78% 83% 76% 80% 76% 88% 75% 82% 84% (58%). The number of treatment courses for the indication AOM was also highest in area V, i.e. 0.88 Participation courses per year per child (Table II). In area E, where the antimicrobial prescription rate was lowest (0.57) in 1998, it had decreased significantly to 0.27 in 2003. 62 55 No. 804 287 889 244 174 331 324 216 The choice of antimicrobial drug also varied

Participants considerably by study areas. Broad-spectrum anti-

microbials (amoxicillin�/clavulanic acid, azitromyzin, erythromycin, trimethoprim-sulphamethoxazole), were used in only 23 of 72 cases (32%) in area E where 6 years / � the total antimicrobial consumption was lowest but 75 66 380 321 198 442 396 256 1.030 1.107 in 148 of 189 cases (78%) in the high-consumption

area V (p /0.0001).

old invited No. B Children 1 6 / Predictors of prescriptions for antibiotics for otitis media � 99 82 As shown in Table III, the child’s age, residence, and 512 300 406 265 2.900 2.004 2.757 1.989 history of tympanostomy tubes (past or present) years old No. Children 1 were independently associated with the number of antimicrobial treatments for AOM. In our 1998 study, this was the case only for age. Smoking did not influence the odds if the child received antimicrobials for AOM or not.

Predictors of tympanostomy tube placements Information about tympanostomy tube usage was obtained for 880 children. A total of 298 (34%)

957 (1) reported tympanostomy tube insertions in one or 4.640 (4) 3.076 (3) 1.094 (1) 4.416 (4) 2.874 (3) 27.013 (17.2) 20.675 (10.2) 28.922 (18.2) 18.203 (9.2) both ears at some time point (cumulative prevalence), and among these, as many as 22% (95% CI

/ positions within parentheses 14�31%) of one-year-old children. Boys, as in 1998, had received tympanostomy tubes significantly more Total no. of inhabitants and no. of GP often (178/467) than girls (120/413) (p�/0.018). The percentage of children who had received tubes varied significantly from 17% in area E to 44% in

area V in 2003 (see Table II, pB/0.0001). Year 1998 2003 2003 2003 2003 2003 From 1998 to 2003, there had been a significant increase in tympanostomy tube placements in areas V and H (where antimicrobial prescription rates were highest), and a decrease in areas E and B (not significant in area B) (see Table II). In area E, a concurrent and significant decrease took place in tympanostomy tube placements among children and Table I. Study population: characteristics of the populations in 2003 and 1998. Area V Vestmannaeyjar 1998 E EgilsstadirB Bolungarvik 1998 Total 1998 H Hafnarfjordur 1998 antimicrobial prescriptions (total use as well as for Association between antibiotic usage for AOM and tympanostomy tube placement 187 Table II. Total number of antimicrobial treatment courses during the 12 months prior to enrolment, number of treatment courses for

AOM, and number (%) of children 1�/6 years of age having had tympanostomy tube placement.

p-value* for changes in No. of treatment courses No. of treatment courses for No. (%) of children having tympanostomy tube per child per year AOM per child per year had tympanostomy tube placement rate between Area Year (95% CI) (95%CI) placement 1998 and 2003

H 1998 1.16 (0.99�/1.33) 0.69 (0.56�/0.83) 81/310 (26.1) 2003 1.05 (0.86�/1.23) 0.57 (0.43�/0.71) 103/280 (36.8) 0.006 V 1998 1.51 (1.26�/1.75) 0.81 (0.62�/1.00) 79/227 (34.8) 2003 1.48 (1.27�/1.69) 0.88 (0.71�/1.04) 143/324 (44.1) 0.034 E 1998 0.89 (0.60�/1.09) 0.57 (0.41�/0.74) 39/148 (26.4) 2003 0.53 (0.41�/0.65) 0.27 (0.19�/0.36) 37/215 (17.2) 0.049 B 1998 1.15 (0.72�/1.57) 0.65 (0.32�/0.99) 17/50 (34.0) 2003 0.72 (0.46�/0.98) 0.41 (0.20�/0.62) 15/61 (24.6) 0.299 Total 1998 1.21 (1.09�/1.32) 0.70 (0.61�/0.79) 216/735 (29.4) 2003 1.06 (0.95�/1.16) 0.60 (0.52�/0.68) 298/880 (33.9) 0.060

Corresponding figures from the 1998 study are included. the indication AOM specifically). According to the area where antimicrobials were most frequently multivariate analysis, adjusted for age, a child having used (area V, Table IV). Day care attendance was tympanostomy tube(s) was more likely to have had also a predictor of having tubes. A significant recurrent antimicrobial treatment and to live in correlation was found at the community level

Table III. Mean number of antimicrobial treatment courses per year for AOM and adjusted odds ratios (OR) for children treated with

antimicrobials for AOM in the preceding 12 months (n�/270), as opposed to not (n�/593).

Mean number of treatment courses Variable per year for AOM (95%CI) OR 95% CI p-value

Age

1�/3 yrs 1.06 (0.90�/1.21) 1 4�/6 yrs 0.23 (0.18�/0.28) 0.18 0.12�/0.25 0.0001

Gender male 0.61 (0.50�/0.72) 1 female 0.59 (0.47�/0.70) 1.01 0.73�/1.40 0.99

Siblings

No 0.82 (0.57�/1.08) 1 Yes 0.55 (0.47�/0.63) 0.79 0.52�/1.20 0.25

Residence

Area V 0.88 (0.71�/1.04) 1 Area E 0.27 (0.19�/0.36) 0.32 0.20�/0.51 0.0001 Area B 0.41 (0.20�/0.62) 0.44 0.22�/0.88 0.019 Area H 0.57 (0.43�/0.71) 0.50 0.34�/0.74 0.0003

Day care No 0.89 (0.58�/1.20) 1 Yes 0.57 (0.49�/0.66) 0.86 0.50�/1.47 0.56

Tympanostomy tube, now or before Yes 0.94 (0.75�/1.13) 1 No 0.43 (0.36�/0.50) 0.49 0.35�/0.70 0.0001

Smoking in the house

No 0.59 (0.50�/0.68) 1 Yes 0.64 (0.45�/0.82) 0.92 0.61�/1.41 0.69

Multivariate analysis (863 cases analysed, data missing for 26 cases). Overall significance: chi-square�/165,79, df�/10, p�/0.0000. 188 V. A. Arason et al. between tympanostomy tube placement rate and Discussion antimicrobial use for AOM (r�/0.97, p�/0.032) Four communities in Iceland have been studied with (Figure 1). an interval of five years with regard to use of antimicrobial drugs, prevalence of tympanostomy Effects of tympanostomy tubes on recent antimicrobial tube placements, and prevalence of penicillin non- drug consumption susceptible pneumococci, in particular to see how Of 123 children having tubes, 49 (40%) had received these factors interact with each other. Our earlier oral antimicrobials at least once during the previous studies have highlighted the risk of recent antimi- 8 weeks, as compared with 124 of 737 children crobial usage on carriage of penicillin non-susceptible pneumococci [1,12] as well as an unusually (17%) without tubes (pB/0.001). Considering only antimicrobial treatment for AMO, 25 children high prevalence of tympanostomy tube placements (20%) in the tympanostomy group had recently in Iceland [2]. In the present paper we observed not received antimicrobials, compared with 74 children only an association between antimicrobial prescription rates for AOM and prevalence of tympanostomy (10%) among those without tubes (pB/0.001). Adjusting for age, the odds ratio for receiving tube placements at the community level, but also antimicrobials was significantly higher for children changes with time between 1998 and 2003 in relation to antimicrobial usage. In the area where with tubes (pB/0.001). In 1998, this difference was not statistically significant. antimicrobial consumption was lowest in 1998, antimicrobial use for AOM as well as tympanostomy tube placements decreased significantly. In the two Parental views on antimicrobial drug treatment areas where antimicrobial use was highest in 1998, Table V gives the results of the questionnaires antimicrobial use remained high, and the tympa- regarding appropriate antimicrobial usage for upper nostomy tube placement rate increased significantly. respiratory infections in children. Data from 1998 Changes in the delivery of acute healthcare services are provided for comparison. At the community in area H from 1998 to 2003 weakened the quality of level, a significant correlation was found between the the local data where a higher antimicrobial prescrip- children’s total antimicrobial use and the rate of tion rate could be expected. parents considering it sometimes appropriate to treat There was a significant association between the common cold with antimicrobials (r�/0.99, p�/ number of antimicrobial prescriptions for AOM in 0.01). children and tympanostomy tube placements on the

Table IV. Odds ratio (OR) adjusted for age for children having tympanostomy tubes (n�/123), as opposed to not (n�/736).

Variable No. OR 95%CI p-value

Residence Area V 314 1

Area E 214 0.35 0.17�/0.64 0.0021 Area B 61 1.02 0.46�/2.24 0.97 Area H 270 0.81 0.50�/1.30 0.38

Number of antimicrobial treatments for AOM, last 12 months 0 594 1 1�/2 203 1.96 1.22�/3.17 0.0059 ]/3 62 4.98 2.60�/9.53 0.0001

Gender Female 407 1 Male 452 1.28 0.84�/1.94 0.25

Smoking in the family house setting No 701 1

Yes 158 1.01 0.60�/1.72 0.95

Day care No 71 1

Yes 788 2.38 1.07�/5.28 0.0317

Multivariate analysis (859 cases analysed, data missing in 30 cases). Overall significance: chi-square�/100.176, df�/9, p�/0.0000. Association between antibiotic usage for AOM and tympanostomy tube placement 189

% received tympanostomy tubes 60

45 Area V 40

35 Area H 30

25 Area B 20 r = 0.97 p = 0.032 15 Area E

0.29 0.33 0.37 0.41 0.45 0.49 0.53 0.57 0.61 0.66 0.70 0.74 0.78 0.82 0.86 Number of antimicrobial courses for AOM per child per year

Figure 1. Correlation between tympanostomy tube placement rate (cumulative prevalence) and antimicrobial use for acute otitis media (last 12 months) among 1- to 6-year-old children in Iceland, 2003. level of both the individual and the community. This placement. A second possibility may be due to the phenomenon may have different underlying expla- fact that otorrhea is a common problem in children nations. One possibility is that frequent use of with tympanostomy tubes [19]. This may lead to antimicrobial drugs might change the bacterial flora prescriptions of antibiotics due to suspicion or fear of in the community, by promoting the emergence of AOM and may at least partly explain why children resistant bacteria [1,12]. This could in turn increase with tubes in the present study had more often the risk of treatment-resistant episodes of bacterial received recent oral antimicrobial treatment. infections including AMO [18], chronic effusion in On the other hand, the observed difference of the middle ear, and subsequent tympanostomy tube practice may have a complex set of explanations.

Table V. Results from parents’ questionnaires regarding appropriate antimicrobial usage for upper respiratory tract infections for children, number and percentage (%), compared with results from the 1998 study.

Question/area Year Always Sometimes Never Don’t know

Question 11 Is it appropiate to give antimicrobial treatment for acute otitis media? Area H 1998 27 (8.3) 286 (87.5) 3 (0.9) 11 (3.4) 2003 30 (10.7) 231 (82.5) 3 (1.1) 16 (5.7) Area V 1998 28 (11.5) 197 (81.1) 4 (1.6) 14 (5.8) 2003 33 (10.2) 274 (85.1) 1 (0.3) 14 (4.3) Area E 1998 9 (5.2) 152 (87.9) 5 (2.9) 7 (4.0) 2003 11 (5.1) 194 (90.7) 1 (0.5) 8 (3.7) Area B 1998 2 (3.6) 51 (92.7) 1 (1.8) 1 (1.8) 2003 1 (1.6) 58 (95.1) 1 (1.6) 1 (1.6) Total 1998 66 (8.3) 686 (86.0) 13 (1.6) 33 (4.1) 2003 75 (8.6) 757 (86.3) 6 (0.7) 39 (4.4)

Question 22 Is it appropriate to give antimicrobial treatment for unspecified upper respiratory tract infection (common cold)? Area H 1998 0 (0.0) 154 (47.2) 148 (45.4) 24 (7.4) 2003 0 (0) 122 (44.0) 137 (49.5) 18 (6.5) Area V 1998 1 (0.4) 121 (49.8) 95 (39.1) 26 (10.7) 2003 0 (0) 186 (57.9) 114 (35.5) 21 (6.5) Area E 1998 0 (0.0) 50 (28.9) 109 (63.0) 14 (8.1) 2003 0 (0) 64 (30.2) 131 (61.8) 17 (8.0) Area B 1998 0 (0.0) 21 (38.2) 25 (45.5) 9 (16.4) 2003 0 (0) 20 (32.8) 38 (62.3) 3 (5.1) Total 1998 1 (0.1) 346 (43.4) 377 (47.3) 73 (9.2) 2003 0 (0) 392 (45.0) 420 (48.2) 59 (6.8)

1 2 1998, Pearson chi-square 13.01, df 9, p�/0.159; 2003, Pearson chi-square 15.05, df 9, p�/0.090. 1998, Pearson chi-square 32.27, df 9, p�/0.0001; 2003, Pearson chi-square 46.65, df 9, p�/0.0001. 190 V. A. Arason et al.

The incidence of respiratory tract infections may [4] Froom J, Culpepper L, Jacobs M, De Melker RA, Green LA, vary between areas. There may also be a tendency to van Buchem L, et al. Antimicrobials for acute otitis media? A review from the International Primary Care Network. BMJ under-diagnose AOM in some areas and over-

1997;315:/ 98/ �/102. diagnose AOM in others. Furthermore, the various [5] Little P, Gould C, Williamson I, Moore M, Warner G, areas may have different treatment traditions/cul- Dunleavey J. Pragmatic randomised controlled trial of two tures in relation to the clinical problem in question. prescribing strategies for childhood acute otitis media. BMJ

A recent study by Gabbay and Le May addressed the 2001;322:/ 336/ �/42. phenomenon of varying clinical ‘‘mindlines’’ among [6] Damoiseaux R, Van Balen F, Hoes A, Verheij T, De Melker R. Primary care based randomised, double blind trial of primary health care practices in the UK [20]. amoxicillin versus placebo for acute otitis media in children Parents in areas where antimicrobial drug usage aged under 2 years. BMJ 2000;320:/ 350/ �/4. was lowest and broad-spectrum antimicrobials [7] Rosenfeld RM, Vertrees JE, Carr J, Cipolle RJ, Uden most rarely prescribed appeared to be better in- DL, Giebink GS, et al. Clinical efﬁcacy of antimicrobial formed about the benefits of restrictive use of drugs for acute otitis media: metaanalysis of 5400 antimicrobial drugs for upper respiratory tract children from thirty-three randomized trials. J Pediatr

1994;124:/ 355/ �/67. infections. These variations in parental attitude [8] Del Mar C, Glasziou P, Hayem M. Are antibiotics indicated may be important as primary care physicians main- as initial treatment for children with acute otitis media? A

tain that parental pressure and expectations in metaanalysis. BMJ 1997;314:/ 1526/ �/9. relation to antimicrobial drug prescriptions represent [9] Van Zuijlen DA, Schilder AG, Van Balen FA, Hoes AW. an important barrier to a restrictive prescribing National differences in incidence of acute mastoiditis: relationship to prescribing patterns of antibiotics for acute practice [2,21�/27].

otitis media? Pediatr Infect Dis J 2001;20:/ 140/ �/4. Our results demonstrate an association between [10] Levy SB. Multidrug resistance: a sign of the times. N Engl J

the use of antibiotics, parental views about antimi- Med 1998;338:/ 1376/ �/8. crobial treatment, and use of tympanostomy tube [11] Molstad S. Reduction in antibiotic prescribing for respira- placements. However, it is impossible to say whether tory tract infections is needed! Scand J Prim Health Care the associations between antimicrobial use for AOM 2003;21:/ 196/ �/8. and tympanostomy tube placements are due to [12] Arason VA, Gunnlaugsson A, Sigurdsson JA, Erlendsdottir H, Gudmundsson S, Kristinsson KG. Clonal spread of direct causal effects or because of differences in resistant pneumococci despite diminished antimicrobial use.

medical practice. The possibility of a direct positive Microb Drug Resist 2002;8:/ 187/ �/92. correlation between antimicrobial drug (over) use [13] Scottish Intercollegiate Guidelines Network (SIGN). Diag- for AOM, future episodes of AOM, and tympanost- nosis and management of childhood otitis media in primary omy tube placement later warrants further investiga- care. A national clinical guideline. Edinburgh (Scotland); tion. February 2003, 18 p. (publication no. 66). Available at: http://www.sign.ac.uk/pdf/sign66.pdf [14] Franklin JH, Marck PA. Outcome analysis of children

receiving tympanostomy tubes. Otolaryngol 1998;27:/ / Acknowledgements 293�/7. [15] Paradise JL, Dollaghan CA, Campbell TF, Feldman HM, The authors would like to thank all the children and Bernard BS, Colborn DK, et al. Otitis media and tympa- parents who participated in the study and the general nostomy insertion during the ﬁrst three years of life: practitioners who assisted in the study areas. This developmental outcomes at the age of four years. Pediatrics study was supported by the Icelandic College of 2003;112:/ 265/ �/77. Family Physicians and the Research Fund of the [16] Gates GA, Avery CA, Prihoda TJ, Cooper JC. Effectiveness of adenoidectomy and tympanostomy tubes in the treatment University of Iceland, Reykjavik.

of chronic otitis media with effusion. N Engl J Med 1987;/

317:1444/ �/51. [17] Schilder AGM, Rovers MM. International perspective on management. In: Rosenfeld RM, Bluestone CD, editors. References Evidence-based otitis media, 2nd ed. Hamilton: BC Decker [1] Arason VA, Kristinsson KG, Sigurdsson JA, Gudmundsson Inc; 2003. p. 325�/33. S, Stefansdottir G, Mo¨lstad S. Do antimicrobials increase [18] Dagan R, Leibovitz E, Cheletz G, Leiberman A, Porat N. the carriage rate of penicillin resistant pneumococci in Antibiotic treatment in acute otitis media promotes super- infection with resistant Streptococcus pneumoniae carried children? Cross sectional prevalence study. BMJ 1996;313:/ /

387�/91. before initiation of treatment. J Infect Dis 2001;183:/ 880/ �/6. [2] Arason VA, Sigurdsson JA, Kristinssson KG, Gudmundsson [19] Ah-Tye C, Paradise JL, Colborn DK. Otorrhea in young S. Tympanostomy tube placements, sociodemographic children after tympanostomy-tube placement for persistent factors and parental expectations for management of middle-ear effusion: prevalence, incidence, and duration.

/ / / acute otitis media in Iceland. Pediatr Infect Dis J 2002;21:/ / Pediatrics 2001;107:1251�8.

1110�/5. [20] Gabbay J, le May A. Evidence based guidelines or collec- [3] McCaig LF, Hughes JM. Trends in antimicrobial drug tively constructed ‘‘mindlines?’’ Ethnographic study of

prescribing among ofﬁce-based physicians in the United knowledge management in primary care. BMJ 2004;329:/ /

States. JAMA 1995;273:/ 214/ �/9. 1013�/6. Association between antibiotic usage for AOM and tympanostomy tube placement 191

[21] Garbutt J, Jeffe DB, Shackelford P. Diagnosis and treatment acute bronchitis in primary care: blinded, randomised

of acute otitis media: an assessment. Pediatrics 2003;112:/ / controlled trial of patient information leaﬂet. BMJ 2002;/

143�/9. 324:91/ �/4. [22] Melander E, Bjorgell A, Bjorgell P, Ovhed I, Mo¨lstad S. [25] Siegel RM, Kiely M, Bien JP, Joseph EC, Davis JB, Mendel Medical audit changes physicians’ prescribing of antibiotics SG, et al. Treatment of otitis media with observation and a

for respiratory tract infections. Scand J Prim Health Care safety-net antibiotic prescription. Pediatrics 2003;112:/ 527/ �/

1999;17:/ 180/ �/4. 31. [23] Munck A, Gahrn-Hansen B, Soegaard P, Soegaard J. Long- [26] Jonsson H, Haraldsson RH. Parents’ perspectives on otitis lasting improvement in general practitioners’ prescribing of media and antibiotics. A qualitative study. Scand J Prim

antibiotics by means of medical audit. Scand J Prim Health Health Care 2002;20:/ 35/ �/9.

Care 1999;17:/ 185/ �/90. [27] Petursson P. GPs’ reasons for ‘‘non-pharmacological’’ pre- [24] Macfarlane J, Holmes W, Gard P, Thornhill D, scribing of antibiotics �/ a phenomenological study. Scand J Macfarlane R, Hubbard R. Reducing antibiotic use for Prim Health Care 2005;23:120�/5. 127

PAPER V

The Role of Antimicrobial Use in the Epidemiology of Resistant Pneumococci: A 10-Year Follow Up

VILHJALMUR A. ARASON,1 JOHANN A. SIGURDSSON,1 HELGA ERLENDSDOTTIR,2 SIGURDUR GUDMUNDSSON,3 and KARL G. KRISTINSSON2,4

ABSTRACT

The relative effects of risk factors on the prevalence of resistant pneumococcal clones are hard to determine. Our aim was to evaluate the effect of risk factors on the prevalence of resistant pneumococci in Iceland in 2003 and compare these data with results of identical studies performed in 1993 and 1998. A randomized sample of 1,107 children was chosen from all 2,532 children 1 to 6 years old living in four communities. Pneu- mococci were carried by 64% of the 824 children enrolled and 9.5% were penicillin nonsusceptible (PNSP), as opposed to 8.1% (1998) and 8.5% (1993), and multiresistant strains of serotype 6B were 2.5% compared to 7.5% and 7.7% (p � 0.001). Antimicrobial use had declined in 10 years from 1.5 to 1.0 courses/child per year. The only significant risk factor for carriage of PNSP and erythromycin-resistant pneumococci was antimicrobial consumption. The multiresistant type 6B strains disappeared from the areas with the lowest antimicrobial use but maintained unchanged prevalence in the area with the highest use. The number of erythromycin-resistant, penicillin-susceptible strains of all pneumococci (37/475, 7.8%) increased significantly from the previous studies (7/353, 2.0%, 1998, and 2/390, 0.5%, 1993). This observation is associated with increased use of macrolides, especially azithromycin, in one of the study areas. Spread of novel resistant clones appears to be the main reason for rapid and significant changes in pneumococcal resistance rates. The choice of antimicrobial class appears to influence the selective environment favoring particular resistant clones.

INTRODUCTION belonged to a single multiresistant clone of serotype 6B (the Spanish-Icelandic clone, Spain-26B).19 An unstructured nation- OMPARATIVE AND ANALYTICAL STUDIES have demonstrated wide campaign to reduce antimicrobial use followed. The cam- Ca relationship between high antimicrobial consumption paign was led by key opinion leaders and involved all of the and increasing antimicrobial drug resistance in pneumo- mass media together with meetings with health professionals. cocci.1,2,12,13,18 However, the effects of reduced antimicrobial Subsequently, the overall antimicrobial use for children reduced consumption and herd immunity on the prevalence of resistance by about one third.2,9 have been harder to document.2 This requires long-term longi- Our studies to evaluate risk factors for PNSP carriage in 1993 tudinal epidemiological studies of risk factors for carriage of and 1998 demonstrated the importance of antimicrobial use, resistant pneumococci and prevalence of resistant clones.10 clonal spread, and herd immunity.1,2 The relative importance There is an increasing need to analyze available data to con- of antimicrobial use compared to clonal spread and herd im- struct mathematical models that can be used as tools to predict munity on PNSP carriage is not known. the likely outcomes of various antibiotic policy options.3,15 The This is the third cross-sectional study of risk factors and incidence of penicillin-nonsusceptible pneumococci (PNSP) in- PNSP carriage in the same communities, giving three snapshots creased rapidly in Iceland from 19897 until 1993, when it had over a 10-year period. Our aim is to analyze the relative effects reached 20% in pneumococcal infections.8 Most of the PNSP of various risk factors, clonal spread, and herd immunity.

1Department of Family Medicine, University of Iceland, Solvangur, Hafnarfjordur, Iceland. 2Department of Clinical Microbiology, Landspitali University Hospital, Reykjavik, Iceland. 3Directorate of Public Health, Reykjavik, Iceland. 4Faculty of Medicine, University of Iceland, Reykjavik, Iceland.

169 170 ARASON ET AL.

MATERIALS AND METHODS The National Bioethics Committee and the National Data Protection Commission approved the study. Study population and design Microbiology Four geographical areas that had been studied in comparative studies in 1993 and 1998 were reexamined in 2003 by com- Nasopharyngeal samples were obtained with rayon-tipped ® parable methods.1,2 At the end of 2002 (December 1, 2002) swabs (Mini-tip Culturette , Becton Dickinson and Co., MD), these areas had a total population of 28,922, including 2,757 stored for a maximum of 24 hr before they were inoculated on children from 1 to 6 years old, i.e., Hafnarfjordur (H), 20,675 blood agar (Difco, Detroit, MI) containing gentamicin (5 mg/L) inhabitants, 2,004 children 1–6 years old. Corresponding fig- and incubated anaerobically. Typical colonies were identified ures for the other areas were Vestmannaeyjar (V), 4,416, 406, with conventional methods, and pneumococci were screened 20 Egilsstadir (E), 2,874, 265, and Bolungavik (B), 957, 82. Area for penicillin resistance by the oxacillin disc diffusion test. If H is a town adjacent to the capital Reykjavik, area V is a fish- colonial appearance suggested the presence of more than one ing town on an island of the south coast, area E is a town sur- pneumococcal strain, each of the colonies was tested separately. rounded by a large farming area, and area B is a fishing town The MIC of nonsusceptible isolates was determined by the E- on the northwest coast. The population density and living stan- test (AB Biodisk, Solna, Sweden) according to the manufac- dards are similar in all the study towns. All eligible children, turer’s recommendations. Isolates having a penicillin MIC of according to the Icelandic National Registry, were invited to �0.094 mg/L were defined as nonsusceptible. Susceptibility to participate in V (396), E (256), and B (75), whereas a random erythromycin, tetracycline, chloramphenicol, clindamycin, and sample of 380 children was invited to participate in area H. trimethoprim-sulfamethoxazole was determined by disc diffu- Eighteen general practitioners, of whom 11 were the same as sion tests according to the Clinical and Laboratory Standards 4 in the 1998 study, served these areas. Institute (CLSI) methods and criteria. Penicillin nonsuscepti- 11 The sites were visited in April and May, 2003. After in- ble isolates were also serotyped by co-agglutination using an- formed parental consent, a nasopharyngeal specimen was taken tisera from the State Seruminstitute (Copenhagen, Denmark). from each child. The parents answered a postal questionnaire Statistical analysis regarding the use of antimicrobials by their child: number of antimicrobial courses in the preceding year; the date and type Carriage of penicillin-nonsusceptible as opposed to -suscep- of the last antimicrobial agent used; type of infection and tible pneumococci or erythromycin-resistant as opposed to ery- whether the child had been taking prophylactic antibiotics �3 thromycin-susceptible pneumococci were the single outcome weeks during the preceding year. They were also asked about variables. Each case could only be associated with a single the presence of tympanostomy tubes (TT) (presently and in the strains, so where there was carriage of a typeable PNSP strain past) and if someone smoked in the same household. Informa- with a nontypeable (nonencapsulated) strain, the nontypeable tion on antibiotic and tympanostomy use was also collected strain was excluded from the analysis because it is much less from the medical records at the local health center. Children likely to be associated with infections. Similarly, we excluded that had received antimicrobial treatment in the preceding 2 penicillin-susceptible strains in dual carriage with PNSP strains. weeks were excluded, as in the previous studies. Analysis of possible association with the outcome variable was:

TABLE 1. ANTIMICROBIAL (AM) USAGE IN NUMBER OF COURSES PER YEAR, CARRIAGE OF PNEUMOCOCCI AND PNSP AND THE NUMBER OF DIFFERENT PNSP STRAINS IN THE STUDY GROUPS

Type of PNSP AM courses Number of per year Number of Number of Non- Area Year Children (�95% CI) PNCa(%) PNSP (%) 6B (%6B) 9V 14 19F 23 typeable

H 1993 527 1.5 (1.4–1.7) 280 53.1 24 8.6 21 7.5 1 2 1998 301 1.0 (0.8–1.1) 174 57.8 11 6.3 9 5.2 1 1 2003 258 1.0 (0.8–1.1) 154 59.7 20 13.0 4 2.6 10 2 4 V 1993 100 1.7 (1.2–2.1) 55 55.0 10 18.2 10 18.2 1998 224 1.4 (1.1–1.6) 122 54.5 5 4.1 5 4.1 2003 301 1.4 (1.2–1.6) 214 71.1 15 7.0 9 4.2 6 E 1993 111 1.3 (1.0–1.6) 52 46.8 1 1.9 1 1.9 1998 167 0.9 (0.7–1.1) 69 41.3 13 18.8 13 18.8 2003 207 0.5 (0.4–0.6) 120 60.0 12 10.0 0 0 5 7 B 1993 53 1.5 (1.0–2.0) 39 73.6 1 2.6 1 2.6 1998 51 1.0 (0.6–1.4) 19 37.3 2 10.5 2 10.5 2003 58 0.7 (0.4–1.0) 37 63.8 3 8.1 0 0 1 2 Total 1993 791 1.5 (1.4–1.6) 426 53.9 36 8.5 33 7.7 1 2 1998 743 1.1 (0.0–1.2) 384 51.7 31 8.1 29 7.5 1 1 2003 824 1.0 (0.9–1.1) 525 63.7 50 9.5 13 2.5 11 5 2 0 19

aPNC, Pneumococcal carriers. EPIDEMIOLOGY OF RESISTANT PNEUMOCOCCI 171 sex, age, area of residence, siblings, day-care attendance, type creased in the other two. The number of serotype 6B strains of the last antimicrobial agent used, weeks from last antimi- had decreased in all areas except area V and the rate of typeable crobial treatment, number of courses in the preceding 12 PNSP had also decreased in all areas (Fig. 1). Nontypeable months, use of prophylactic antibiotics, use of tympanostomy (nonencapsulated) PNSP strains had not been observed in the tubes at the time of sampling or before, and tobacco smoking two previous studies. in the same household. The Pearson chi-square tests were used Carriage of erythromycin-resistant pneumococci: The num- for univariate analysis of categorical variables and one-way ber of erythromycin-resistant and penicillin-susceptible strains analysis of variance (ANOVA) for continuous variables. increased significantly from the previous study in 1998 in ar- As in the earlier studies of 1993 and 1998, the multivariate eas H and V (p � 0.0004 and p � 0.0001, respectively), but de- logistic regression method was used to estimate the risk for all creased in the other two areas (E and B, p � 0.05 and p � 0.6, known variables of carrying PNSP to control interdependence. respectively) (see Table 2). However, the proportion of ery- Individual regression coefficients were tested with the Wald sta- thromycin resistance among PNSP remained similar. tistic, and confidence intervals calculated for the odds. The mul- Antimicrobial use: The mean number of antimicrobial tivariate analyses were performed with the SPSS® program for courses per child in the study population was 1.0 during the Windows (Advanced Statistics Release 8.0, SPSS Inc, Chicago, year preceding the sampling (CI 0.9–1.1; 33.3% reduction from IL). The level of statistical significance was 0.05. Confidence 1993 and 9.1% from 1998, Table 1 and Fig. 1). Forty six per- intervals are given as 95% confidence intervals. cent of the children (n � 379) had received antimicrobials at least once during the preceding year, compared to 65% in 1993 and 40% in 1998. The consumption was lowest in area E and highest in area V. As previously, acute otitis media was the RESULTS

Nasopharyngeal carriage TABLE 2. ERYTHROMYCIN SUSCEPTIBILITY OF PENICILLIN- Overall carriage: Of the 1,107 children invited, 848 (77%) SUSCEPTIBLE AND NONSUSCEPTIBLE PNEUMOCOCCI, IN 1993, participated (H, 74%; V, 78%; E, 82%, and B 79%). Twenty 1998, AND 2003, IN THE RESPECTIVE AREAS (NUMBER OF four were excluded from nasopharyngeal culturing because they ERYTHROMYCIN-RESISTANT PNEUMOCOCCI) had received antimicrobials in the 2 preceding weeks. Thus, 824 children were studied. The mean age for the whole group Number a was 4.3 years (SD � 1.7) (H, 4.2; V, 4.4; E, 4.2, and B, 3.9). Area Year Number of ERY % A total of 525 carried pneumococci (63.7%) and average car- H PSPb 1993 256 0 0 riage rate in the communities varied from 59.7% to 71.1% 1998 163 1 0.6 (Table 1). 2003 134 13 9.7 Carriage of PNSP: The proportion of PNSP was 9.5%, but PNSP 1993 24 20 83.3 only 5.9% if nontypeable strains are excluded (Table 1). Mul- 1998 11 7 63.6 tiresistant serotype 6B strains (n � 13) (phenotypically identi- 2003 20 10 50.0 cal to the Spanish-Icelandic clone) were only found in two V PSP 1993 45 2 4.4 areas (Table 1). Fifty four children carried at least two pneu- 1998 117 0 0 mococcal strains. In two instances, children carried two PNSP 2003 199 21 10.6 strains where one was nontypeable and therefore excluded from PNSP 1993 10 9 90.0 statistical analyses and Table 1. Similarly, we excluded 9 peni- 1998 5 5 100 2003 15 14 93.3 cillin-susceptible strains in dual carriage with PNSP nontype- E PSP 1993 51 0 0 able strains and 12 penicillin-susceptible strains in dual carriage 1998 56 4 7.1 with PNSP typeable strains. Thirty-one children carried two or 2003 108 1 0.9 more penicillin-susceptible pneumococci. Two children carried PNSP 1993 1 1 100 only penicillin-susceptible nontypeable pneumococci. All of the 1998 13 13 100 PNSP were resistant to trimethoprim-sulfamethoxazole and all 2003 12 8 66.7 type 6B, type 19F, and nontypeable strains were multiresistant. B PSP 1993 38 0 0 All except the serotype 6B strains were susceptible to chlo- 1998 17 2 11.8 ramphenicol. The serotype 9V and 14 strains were susceptible 2003 34 2 5.9 to erythromycin, tetracycline, and clindamycin but the nonty- PNSP 1993 1 1 100 1998 2 2 100 peable and serotype 6B strains were not. The penicillin MICs 2003 3 2 66.7 were as follows: serotype 6B, nine strains 0.25 mg/L, three 0.38 mg/L, and one 0.75 mg/L; serotype 9V, one 0.125 mg/L, two Total PSP 1993 390 2 0.5 0.25 mg/L, four 0.38 mg/L, and four 0.5 mg/L; serotype 14, 1998 353 7 2 three 0.5 mg/L, one 0.75 mg/L, and one 1.0 mg/L; serotype 2003 475 37 7.8 PNSP 1993 36 31 86.1 19F, one 0.25 mg/L and one 0.5 mg/L; nontypeable (nonen- 1998 31 27 87.1 capsulated) strains, five 0.094, one 0.19 mg/L, eight 0.25 mg/L, 2003 50 34 68.0 three 0.38 mg/L, and one 0.5 mg/L. There was a marked difference in the PNSP rates between the study areas (7.0–13.0%, aERY, Erythromycin. Table 1), which had decreased from 1998 in two areas but in- bPSP, Penicillin-susceptible pneumococci. 172 ARASON ET AL.

Age: The mean age for children carrying pneumococci was lower, 4.12 years (CI 3.98–4.26), than for children not carrying pneumococci, 4.49 years (CI 4.29–4.69), but not significantly lower for PNSP carriage. The PNSP carriage rate was highest for 2-year-children, 18% (16/89); 8.3% for 1 year, 9% for 3 years, 7.4% for 4 years, 6.1% for 5 years, and 8.3% for 6-year- old children. The carriage of specific serotypes/groups of PNSP was not related to particular age groups, except that carriers of nontypeable pneumococci were significantly older than carriers of serotype 14 (mean age 4.08 years (95% CI 3.22–5.00) as opposed to 2.82 (2.57–3.08). The mean age was 3.95 years (2.70–5.19) for type 6B and 3.41 (2.50–4.31) for type 9V. Tympanostomy tubes: Information on tympanostomy tube use was available for 817 children; thereof 279 (34%) children either currently had tubes or had had tubes before. Information on current use was available for 782, and of these as many as 111 (14.2%) had tympanostomy tubes at the time of sampling. Presence of tympanostomy tubes was neither associated with carriage of pneumococci nor PNSP (Table 3). Smoking: Pneumococcal carriage was slightly higher in children from smoking households as opposed to nonsmoking FIG. 1. The proportion of PNSP (typeable and nontypeable, households, but the difference was not significant (100/522 for typeable strains only, and serotype 6B only), and antimicrobial carriers vs. 48/297 for others, p � 0.30). There was no associ- use in the years 1993, 1998, and 2003. ation between smoking in the household settings and PNSP carriage (Table 3). Other factors: Children attending day care were more likely to carry pneumococci 489/752 than children not attending day most common reason for antimicrobial prescriptions (56%). An- care 35/70 (p � 0.0138), but pneumococcal carriage was nei- timicrobial use by age was 1.82 courses per one year old child ther associated with gender nor to number of siblings. per year (CI 1.36–2.28), 1.94 (1.56–2.33) for 2 years old, 1.17 Factors that were not found to be significantly associated (0.96–1.38) for 3 years old, 0.76 (0.58–0.94) for 4 years old, with PNSP carriage (Table 3) were gender, number of siblings, 0.46 (0.32–0.61) for 5-year-old, and 0.35 (0.23–0.48) for 6- and day-care attendance. year-old children. The choice of antimicrobial class differed Multivariate analysis: To control for confounding factors, all markedly between areas. Amoxicillin was the most commonly significant variables from the univariate analysis were used in prescribed antimicrobial agent overall 29% (37% in 1998 and a multivariate backward stepwise logistic regression model 20.8% in 1993), and in all areas except area V (E, 43%; B, (number of children in analysis � 506, �2 � 10.412, df � 1, 32%; H, 39%, and V, 17%). The penicillins (amoxicillin, amox- p � 0.013). The number of antimicrobial treatments was the icillin � clavulanic acid, and phenoxmethylpenicillin) ac- only independent risk factor for carriage of PNSP, odds ratio counted for 62% overall (B, 82%; H, 75%; E, 77%; and V, 1.28 for each treatment (95% CI 1.11–1.48), p � 0.007. Figure 46%). Other antimicrobials accounted for less than 15% in all 2 shows the odds ratio by using a similar multivariate logistic areas except area V. The main antimicrobial used in area V was model for different variables in the 1993, 1998, and 2003 stud- azithromycin (33.3%), which was rarely used in the other ar- ies, where the number of weeks from last antimicrobial courses eas (E 1.5%, B 13.6%, and H 9.7%). is used in the models instead of the number of antimicrobial Factors associated with carriage of PNSP courses in the preceding 12 months. The time duration of 2–7 weeks from last antimicrobial treatment compared to �8 weeks Antimicrobial use: Antimicrobial use was the most significant was the only significant risk factor for PNSP carriage in all the risk factor for carrying PNSP by univariate analysis (Table 3). three analyses. Children carrying PNSP had received on average 1.78 Factors associated with carriage of erythromycin-resistant antimicrobial courses during the preceding 12 months (CI pneumococci: All of the variables tested for association with 1.24–2.32) compared to 0.95 courses (CI 0.82–1.09) for children carriage of PNSP were also tested for association with carriage carrying penicillin-susceptible pneumococci (Table 3) and 0.93 of erythromycin-resistant pneumococci with multivariate back- (CI 0.75–1.10) for no carriage. The PNSP carriage rate was 26.7% ward stepwise logistic regression model (number of children in (16/60) 2–7 weeks after antimicrobial treatment compared to 7.3% analysis � 524, �2 � 5.35, df � 1, p � 0.027). As for PNSP (34/465) �8 weeks after treatment (p � 0.001). On the other hand, carriage, the number of antimicrobial treatments was the only the overall pneumococcal carriage was similar for children that independent risk factor for carriage of erythromycin-resistant had received antimicrobial treatment 2–7 weeks before sampling pneumococci, odds ratio 1.18 for each treatment (95% CI time (60/104, 58%) as opposed to �8 weeks before sampling time 1.03–1.35), p � 0.0157. The association of using a particular (465/720, 64%)(p � 0.1906). There was no significant difference antimicrobial class was compared with using any other class or in the recorded risk factors between children carrying typeable no antibiotic. By testing the risk of using a particular antimi- PNSP versus nontypeable PNSP (Table 4). crobial class versus not having used an antimicrobial agent, the EPIDEMIOLOGY OF RESISTANT PNEUMOCOCCI 173

TABLE 3. UNIVARIATE ANALYSIS ON DIFFERENT VARIABLES FOR CHILDREN CARRYING PNSP COMPARED TO CHILDREN CARRYING PENICILLIN-SUSCEPTIBLE PNEUMOCOCCI Penicillin- Number susceptible Variable children pneumococci PNSP p value

Residence Area H 258 134 20 0.280 Area V 301 199 15 Area E 207 108 12 Area B 58 34 3 Age Mean 4.16 Mean 3.78 (95% CI 4.01–4.30) (95% CI 3.03–4.25) Sex Male 430 249 29 0.462 Female 394 226 21 Number of Mean 1.40 Mean 1.63 siblings (95% CI 1.30–1.50) (95% CI 1.31–1.95) Day-care Yes 752 443 46 attendance No 70 31 4 0.764 Smoking in the Yes 148 94 6 household No 671 378 44 0.255 Tympanostomy Yes 279 169 20 tubes at No 689 391 37 0.175 sampling time Number of Mean 0.95 Mean 1.78 �0.001 antimicrobial (95% CI 0.82–1.09) (95% CI 1.24–2.32) (AM) courses last 12 months Number of weeks Mean 21.50 Mean 10.82 �0.001 from last AM (95% CI 19.46–23.53) (95% CI 7.58–14.06) treatment Prophylactic Yes 12 2 AM last 12 No 460 48 0.635 months Type of last AM Amoxicillin 105 52 (25.9%) 12 (34.3%) 0.938 Amox.-clav.acid 87 49 (24.4%) 13 (37.1%) 0.144 Fenox.m.pc. 32 15 (7.5%) 1 (2.9%) 0.478 Trimethophrim- 23 14 (7.0%) 1 (2.9%) 0.705 sulpha Erythromycin 20 13 (6.5%) 0 Azithromycin 71 41 (20.4%) 6 (17.1%) 0.820 Cefuroxime 6 5 (2.5%) 0 Cefalexin 9 5 (2.5%) 1 (2.9%) 1.000 Dicloxacillin 8 7 (3.5%) 1 (2.9%) 1.000

use of macrolides and amoxicillin � clavulanic acid was asso- (8.5, 8.1, and 5.9% respectively). The association between the ciated with carriage of erythromycin-resistant pneumococci rates of antimicrobial use and resistance is not surprising, and (p � 0.081 and p � 0.043, respectively), but not the other in that sense these studies do little but confirm previous stud- classes. ies. However, the design of our studies allows us to look at the changes within individual communities at different times. There are much greater changes taking place within the in- DISCUSSION dividual communities, changes that may be difficult to explain by antimicrobial use alone. In 1998, there was marked increase Observing the rates of PNSP together with antimicrobial use in PNSP rates in the two communities, which had had the low- at three occasions over a 10-year period in four communities est PNSP rates in 1993, despite significant decrease in antimi- in different parts of Iceland gives important clues regarding the crobial use. The increase was only due to an increase in mul- epidemiology of PNSP. Antimicrobial use was highest at the tiresistant serotype 6B strains (representative phenotypically first study in 1993 (1.5 AM courses/child per year) and had identical strains have previously been shown to belong to the come down by a third at the last study in 2003. At the same Spanish Icelandic clone, i.e., Spain6B-2)16,19 and was explained time, there was little overall change in the rates of PNSP (8.5, by clonal spread into “virgin” communities.2 The current study 8.1, and 9.5% respectively), yet by excluding nontypeable pneu- does indeed support that explanation, as that serotype (clone) mococci the PNSP rate has also come down by almost a third has now disappeared from these two communities, probably due 174 ARASON ET AL.

TABLE 4. ASSOCIATION OF POTENTIAL RISK FACTORS WITH CARRIAGE OF TYPEABLE AND NONTYPEABLE (NONENCAPSULATED) PNSP Typeable Nontypeable Variable PNSP PNSP p value

Age Mean 3.18 Mean 3.77 (95% CI 2.64–3.72) (95% CI 2.63–4.90) Gender Male 18 11 1.000 Female 13 8 Number of siblings Mean 1.18 Mean 2.08 (95% CI 0.86–1.51) (95% CI 1.13–3.04) Daycare attendance Yes 29 17 0.629 No 2 2 Smoking in the household Yes 3 3 0.661 No 28 16 Tympanostomy tubes Yes 13 7 0.774 anytime No 18 12 Tympanostomy tube at Yes 7 3 0.727 sampling time No 23 14 Prophylactic antimicrobial Yes 2 0 (AM) last 12 months No 29 19 Number of AM courses last Mean 2.36 Mean 2.33 12 months (95% CI 1.66–3.07) (95% CI 1.71–2.96) Number of weeks from last Mean 11.64 Mean 9.33 AM treatment (95% CI 7.00–16.27) (95% CI 5.00–13.66) to increased herd immunity to that particular clone and reduced tect in large populations, yet similar changes took place with antimicrobial use. The five yearly data are demonstrated in Fig. Streptococcus pyogenes clones in Finland.6 We can also state 3A and the proposed prevalence of the Spanish-Icelandic clone that the time period from the onset to the end of the epidemic with time in the different areas in Fig. 3B. Therefore, it is rea- wave for a particular clone is less than 10 years. In addition, it sonable to state that clonal spread in specific geographical ar- is likely that the extent of antimicrobial use will determine both eas can have more profound effects on the rates of PNSP than the peak prevalence and the subsequent endemic prevalence. antimicrobial use. Such changes may be more difficult to de- Pneumococcal vaccination has not been recommended for chil-

FIG. 2. Odds ratio for carrying PNSP as opposed to susceptible pneumococci, according to multivariate logistic regression analysis for the 1993, 1998, and 2003 studies. TT, Tympanostomy tubes. EPIDEMIOLOGY OF RESISTANT PNEUMOCOCCI 175

FIG. 3. The proportion of multiresistant serotype 6B strains (phenotypically identical to the Spanish-Icelandic clone) in the different areas in 1993, 1998, and 2003 (A), and the postulated epidemic curves for the Spanish-Icelandic clone in the four study areas (B). dren in Iceland, unless they belong to specific risk groups. Very cocci colonizing children attending day-care centers in Lisbon, few children have been vaccinated with the new conjugate vac- Portugal, 7.4% were nontypeable, but after retesting and PCR cines, and therefore vaccinations should not play a role in the of the lytA and psaA genes the true nontypeable rate was 5.9%. changing epidemiology. This rate had increased from 3.8% in 1997 to 11% in 1999 and The Spanish Icelandic clone appears to have disappeared the strains were genetically diverse, although a dominant clone from two of the communities (B and E), continued to decline accounted for about half the strains. Most of the strains (86%) in one (H), but surprisingly remained stable in one community were resistant to antibiotics.17 Another recent study of 121 non- (V). This cannot be explained by lack of herd immunity, be- typeable strains from Finland, also showed genetic diversity, cause the clone has been present in that area at least since 1993. yet the majority belonged to a single lineage with defective cap- The continued high antimicrobial use in the area could perhaps sular locus. Comparison with the multilocus sequence typing explain why the clone is still present in 2003 and it is tempt- database showed that strains of that lineage have spread inter- ing to conclude that rapidly increasing use of azithromycin (one continentally.14 The significance of penicillin nonsusceptibility third of all prescriptions in 2003, and much higher than in the in the nontypeable pneumococci is not clear. Although such other areas) has established a favorable selective environment strains have lost their main virulence determinant, they may still for this macrolide-resistant clone. This environment may also be important as reservoirs of resistance genes. have led to the marked increase in the number of erythromycin- Although the three studies only give three snapshots of the resistant and penicillin-susceptible pneumococci in that area. resistance situation, we have reliable information about the an- In fact, the long half-life and low serum concentrations of timicrobial use in the study areas in the years preceding the azithromycin have been associated with increased resistance snapshots and could sample at least 74% of the children in the rates.5 study areas, giving very representative snapshots. Adding fur- The nontypeable pneumococci all had a rough appearance ther strength to the studies was having the same investigators and are probably nonencapsulated, although this has not been take all of the nasopharyngeal samples in all areas for all of the confirmed with molecular investigations. Such rough (nonen- studies, and the same biomedical laboratory scientists inocu- capsulated) strains had not been observed in the previous two lating and reading most of the agar plates. studies. It is unlikely that such rough strains were missed in the In conclusion, for small communities, the spread of resistant previous studies because all the agar plates from the 1998 and clones appears to be the main reason for rapid and significant 2003 studies were read by the same senior biomedical labora- changes in pneumococcal resistance rates. Recent antimicrobial tory scientist, and their appearance in 2003 could indicate the use is the most consistent and important risk factor for carriage introduction of novel clone(s). In a recent study of pneumo- of resistant pneumococci and the choice of antimicrobial class 176 ARASON ET AL. may influence the selective environment favoring particular re- (ed.), Streptococcus pneumoniae. Molecular biology and mecha- sistant clones. nisms of disease. Mary Ann Liebert Inc., New York, pp. 419–425. 11. Kronvall, G. 1973. A rapid slide-agglutination method for typing pneumococci by means of a specific antibody adsorbed to protein- A-containing staphylococci. J. Med. Microbiol. 6:187–190. ACKNOWLEDGMENTS 12. Melander, E., K. Ekdahl, G. Jonsson, and S. Molstad. 2000. Frequency of penicillin-resistant pneumococci in children is cor- We extend special thanks to all of the children who partici- related to community utilization of antibiotics. Pediatr. Infect. Dis. pated in the study, their parents, the general practitioners who as- 19:1172–1177. sisted in the study areas, and to the staff of the Department of 13. Melander, E., S. Molstad, K. Persson, H.B. Hansson, M. Soder- Clinical Microbiology, Landspitali University Hospital. This strom, and K. Ekdahl. 1998. Previous antibiotics consumption study was supported by the Icelandic College of Family Physi- and other risk factors for carriage of penicillin-resistant Strepto- cians, The Research Fund of the University of Iceland, and the coccus pneumoniae in children. Eur. J. Clin. Microbiol. Infect. Dis. Research Fund of the Landspitali University Hospital, Reykjavik. 17:834–838. 14. Hanage, W.P., T. Kaijalainen, A. Saukkoriipi, J.L. Rickcord, and B.G. Spratt. 2006. A successful, diverse disease-associated lineage of nontypeable pneumococci that has lost the capsular REFERENCES biosynthesis locus. J. Clin. Microbiol. 44:743–749. 15. Huovinen, P. 2005. Mathematical model-tell us the future! J. An- 1. Arason, V.A., K.G. Kristinsson, J.A. Sigurdsson, G. Stefans- timicrob. Chemother. 56:257–258. dottir, S. Molstad, and S. Gudmundsson. 1996. Do antimicro- 16. Sa-Leao, R., S.E. Vilhelmsson, H. de Lencastre, K.G. Kristins- bials increase the carriage rate of penicillin resistant pneumococci son, and A . Tomasz. 2002. Diversity of penicillin-nonsuscepti- in children? Cross sectional prevalence study. Br. Med. J. ble Streptococcus pneumoniae circulating in Iceland after the in- 313:387–391. troduction of penicillin-resistant clone Spain(6B)-2. J. Infect. Dis. 2. Arason, V.A., A. Gunnlaugsson, J.A. Sigurdsson, H. Erlends- 186:966–975. dottir, S. Gudmundsson, and K.G. Kristinsson. 2002. Clonal 17. Sa-Leao, R., A.S. Simoes, S. Nunes, N.G. Sousa, N. Frazao, and spread of resistant pneumococci despite diminished antimicrobial H. de Lencastre. 2006. Identification, prevalence and population use. Microb. Drug. Resist. 8:187–192. structure of non-typeable Streptococcus pneumoniae in carriage 3. Austin, D.J., K.G. Kristinsson, and R.M. Anderson. 1999.The samples isolated from preschoolers attending day-care centres. Mi- relationship between the volume of antimicrobial consumption in crobiology 152:367–376. human communities and the frequency of resistance. Proc. Natl. 18. Seppala, H., T. Klaukka, J. Vuopio-Varkila, A. Muotiala, H. Acad. Sci. USA. 96:1152–1156. Helenius, K. Lager, and P. Huovinen. 1997. The effect of changes 4. Clinical and Laboratory Standards Institute. 2006. Performance in the consumption of macrolide antibiotics on erythromycin re- Standards for antimicrobial susceptibility testing. CLSI document sistance in group A streptococci in Finland. N. Engl. J. Med. M100-S16 [ISBN 1-56238-588-7]. Clinical and Laboratory Stan- 337:441–446. dards Institute, PA 19087-1898 USA. 19. Soares, S., K.G. Kristinsson, J.M. Musser, and A. Tomasz. 5. Kastner, U., and J.P. Guggenbichler. 2001. Influence of 1993. Evidence for the introduction of a multiresistant clone of macrolide antibiotics on promotion of resistance in the oral flora serotype 6B Streptococcus pneumoniae from Spain to Iceland in of children. Infection 29:251–256. the late 1980s. J. Infect. Dis. 168:158–163. 6. Kataja, J., P. Huovinen, A. Muotiala, J. Vuopio-Varkila, A. Ef- 20. Swenson, J.M., B.C. Hill, and C. Thornsberry. 1986. Screen- stratiou, G. Hallas, and H. Seppala. 1998. Clonal spread of group ing pneumococci for penicillin resistance. J. Clin. Microbiol. A streptococcus with the new type of erythromycin resistance. 24:749–752. Finnish Study Group for Antimicrobial Resistance. J Infect. Dis. 3:786–789. 7. Kristinsson, K.G., M.A. Hjalmarsdottir, and O. Steingrimsson. Address reprint requests to: 1992. Increasing penicillin resistance in pneumococci in Iceland. Dr. Karl G. Kristinsson Lancet 339:1606–1607. Department of Clinical Microbiology 8. Kristinsson, K.G. 1995. Epidemiology of penicillin resistant pneu- Landspitali University Hospital mococci in Iceland. Microb. Drug Resist. 1:121–125. 9. Kristinsson, K.G. 1999. Modification of prescribers’ behavior: the v/Baronstig Icelandic approach. Clin. Microbiol. Infect. 5 (suppl. 4):43–47. 101 Reykjavik, Iceland 10. Kristinsson, K.G. 2000. Effect of antimicrobial use and other risk factors on antimicrobial resistance in pneumococci. In A.Tomasz E-mail: [email protected] 137 APPENDIX

Informed parental consent and questionnaire 2003.

Upplýsingar um rannsóknina: Sýklalyfjanotkun og ónæmar bakteríur í nefkoki barna

Ábyrgðamaður: Vilhjálmur Ari Arason, heimilislæknir, Heilsugæslu stöðinni Sólvangi, Hafnarfirði (Sími: 550 26 70, GSM: 8959156 ). (Aðrir umsjónarmenn og samstarfsaðilar: Prófessor Jóhann Ágúst Sigurðsson, Heimilislæknisfræði, Lækna deild Háskóla Íslands, Dr. Sigurður Guðmundsson, landlæknir og prófessor Karl G.Kristinsson, sýklafræðingur, Landsspítala-Háskólasjúkrahús. Rannsóknin er gerð í samvinnu við lækna heilsugæslustöðvarinnar).

Tilgangur og ávinningur rannsóknarinnar: Tíðni baktería sem eru ónæmar fyrir sýklalyfjum fer vaxandi, einkum svonefndra pneumó kokka í nefkoki barna. Margar rannsóknir (meðal annars þær sem gerðar voru í Vestmannaeyjum, Egilsstöðum, Bolungarvík og í Hafn arfirði á árunum 1993 og 1998), sýna tengsl milli þessarar þróunar og mikillar notkunar á sýklalyfjum. Tilgangur rannsóknar nú er að endurtaka fyrri rannsóknir hér á landi 5 árum eftir síðustu rannsókn. Ræktaðar verða bakteríur úr nefkoki barna á aldrinum 1-6 ára með því að taka strok úr nefi með bómullarpinna, fengnar upplýsingar um sýk- ingar og notkun sýklalyfja, samkvæmt spurningablaði og samkvæmt upplýsingum úr sjúkraskrá heilsugæslustöðvarinnar. Markmiðið er sem fyrr að skoða árangur fyrri úrlausna og finna ða ferðir til þess að minnka ört vaxandi tíðni ónæmra bakteríustofna gegn sýklalyfjum.

Þátttaka barns felst í því að: 1) Foreldri fyllir út í spurningalista þar sem spurt er m.a um sýkla lyfjanotkun barnsins, (verður einnig athugað í sjúkraskrá), notkun röra í hljóðhimnur og viðhorf foreldis til sýklalyfjanotkunar. 2) Stroksýni verður tekið úr nefi barnsins með bómullarpinna sem er barninu að skaðlausu og án teljandi óþæginda (e.t.v smá kláði í nefi á eftir og hnerri). Sýnatakan er framkvæmd í leikskólunum eða skólanum af rannsókn araðilum (ef foreldri er búið að samþykkja þátttöku skriflega) eða á Heilsugæslustöðinni ef foreldri óskar eftir. 138 Stroksýnið er sent til Sýkladeildar Landspítala-Háskólasjúkrahúss og eingöngu notað til ræktunar á bakteríum og athugun á hugsanlegu ónæmi þeirra gegn sýklalyfjum.

Viðkomandi heilsugæslulæknar fá sent bréf ef barn greinist með penicíllin ónæman pneumókokk (foreldrar geta fengið upplýsingar hjá þeim ef um er að ræða spurningu um meðhöndlun á efri loftvega sýkingum með sýklalyfjum). Persónuupplýsingum sem ekki tilheyra sjúkraskrá barnsins verður eytt að lokinni úrvinnslu innan 2ja ára frá sýnatökunni. Fyllsta trúnaðar verður gætt hvað varðar allar upplýsingar sem aflað verður. Farið verður með persónuupplýsingar og skráningu þe- irra í samræmi við lög um persónuvernd nr. 77/2000. Rannsóknin hefur jafnframt hlotið leyfi Vísindasiðanefndar og Persónuverndar. Úrvinnsla gagna er í höndum umsjónarmanna og fer eingöngu fram innanlands. Niðurstöður rannsókna verða eingöngu birtar fyrir hópa og ekki persónugreinanlegar. Tekið skal fram að rannsóknin beinist ekki að erfðaefnum eða ættartengslum. Forráðarmönnum er hvenær sem er heimilt að afturkalla samþyk- ki til þátttöku í rannsókninni. Gögnum um barnið sem tilheyra þessa- ri rannsókn verður þá eytt. Hætti barn þátttöku mun það ekki í neinu tilviki skerða þá heilbrigðisþjónustu sem barninu stendur annars til boða í heilsugæslunni. Ef þú hefur spurningar um rétt þinn sem þátttakandi í vísinda- rannsókn eða vilt hætta þátttöku í rannsókninni getur þú snúið þér til Vísindasiðanefndar, Laugavegi 103, 105 Reykjavík. Sími: 551- 7100, fax: 551-1444 139 Samþykki foreldris um þátttöku barnsins:

Kæru foreldrar Erindi bréfsins er að leita eftir þátttöku barns yðar í rannsókn sem felst í því að taka nefstrok úr barninu, svara spurningalista og skoðun sjúkraskrár samkvæmt nánari lýsingum á meðfylgjandi upplýsingablaði sem foreldri/forráðamaður heldur eftir fyrir sig.

Rannsóknin er framkvæmd á leikskólum/skólum bæjarins og Heilsu gæslustöðinni, á tímabilinu 31. mars - 9. apríl 2003.

Foreldrar sem samþykkja þátttöku eru góðfúslega beðnir um að straðfesta það með undirskrift sinni hér að neðan og að svara meðfylgjandi spurningalista.

Blaðinu með spurningalistanum má síðan skila til leikskóla/skóla barnsins eða á Heilsugæslustöðina ef barnið kemur til sýnatöku þar.

nafn barns:______kt.______sími:______nafn foreldris/ forráðamanns:______kt. ______

Dagsetning samþykkis:______/ ______2003

Fyrir hönd rannsóknarhóps,Vilhjálmur Ari Arason, læknir

Ef þú hefur spurningar um rétt þinn sem þátttakandi í vísinda- rannsókn eða vilt hætta þátttöku í rannsókninni getur þú snúið þér til Vísindasiðanefndar, Laugavegi 103, 105 Reykjavík. Sími: 551-7100, fax: 551-1444. 140 Spurningalisti (krossið við eða svarið spurningum eftir sem við á)

Aldur foreldris/forráðamanns sem svarar spurningum ____ ára

Karl ❏ Kona ❏

Svarið hvað ykkur finnst réttast: Á að meðhöndla eyrnabóglur með sýklalyfjum?

Alltaf ❏ Stundum ❏ Aldrei ❏ Veit ekki ❏

Á að meðhöndla kvef með sýklalyfjum?

Alltaf ❏ Stundum ❏ Aldrei ❏ Veit ekki ❏

Takið afstöðu til neðangreindra fullyrðinga: Sumir sýklar (bakteríur) eru að verða ónæmir fyrir sýklalyfjum.

Sammála (já) ❏ Hlutlaus ❏ Ósammála (nei) ❏ Veit ekki ❏

Ofnotkun sýklalyfja getur leitt til þess að þau tapi virkni sinni.

Sammála (já) ❏ Hlutlaus ❏ Ósammála (nei) ❏ Veit ekki ❏ 141

Er barnið í dagvistun/leikskóla/skóla: Já ❏ Nei ❏

Nafn á leikskóla/skóla: ______

Fjöldi systkina á heimilinu? ______

Hve oft hefur barnið fengið sýklalyf sl 12 mán? ______

Ástæður og fjöldi sýklalyfjameðferða sl. 12 mán. (skrifið fjölda meðferða fyrir aftan sjúkdómsgreiningu eftir því sem við á):

Hálsbólga ______Skútabólga (kinnholubólga)______Eyrnabólga ______Húðsýking ______Berkjubólga ______Þvagfærasýking ______Lungnabólga ______Aðrar ástæður ______

Barnið verið á samfeldri sýklalyfjameðferð (3 vikur eða lengur samfellt) sl. 12 mán.? já ❏ nei ❏

Ef já, hvers vegna (við hverskonar sýkingu)? ______

Ef barn hefur fengið sýklalyfjameðferð á árinu, hvað eru marg ar vikur frá síðustu meðferð? ______vikur Eða Er barnið á sýklalyfjameðferð nú, hvað hefur sýklalyfjameðferð þá staðið í marga daga? ______dagar

Ef barn hefur fengið sýklalyf sl. 12 mán., hver var ástæða fyrir síðustu sýklalyfjameðferð barnsins? ______og hvaða sýklalyf fékk barnið þá? ______

142 Hafa kokkirtlar (nefkirtlarnir) verið fjarlægðir úr barninu?

Já ❏ Nei ❏ Veit ekki ❏

Ef já, þá hver/hvar/hvenær______

Hafa hálseitlar/hálskirtlar (tonsillur) verið frjarlægðir?

Já ❏ Nei ❏ Veit ekki ❏

Ef já, þá hver/hvar/hvenær______

Hversu oft að meðaltali fór barnið þitt í sund á aldrinum a) 0 – 1 árs?: ______sinni á ári b) 1 – 2 ára?: ______sinni á ári c) 2 – 3 ára?: ______sinni á ári d) 3 – 4 ára?: ______sinni á ári e) 4 – 5 ára?: ______sinni á ári f) 5 – 6 ára?: ______sinni á ári g) 6 – 7 ára?: ______sinni á ári

Aldur við fyrstu sundferðir? ______ára

Er reykt á heimilinu?

Já ❏ Nei ❏ 143 Hefur barnið þitt einhven tíman haft rör í eyrum?

Já ❏ Nei ❏ Veit ekki ❏

Ef já, hversu gamalt var það þegar það fékk fyrst rör? ______ára

Hefur barnið þitt rör í eyra núna?

Já ❏ Nei ❏ Veit ekki ❏

Ef já við spurningu hvort barnið sé með eða hafi verið með rör vin samlega svarið eftirtöldum spurningum: Geturðu nefnt helstu ástæðurnar fyrir rörísetningu að þínu mati (Má merkja við fleiri en einn, gjarnan forgangsraða fyrstu 3 frá 1-3) a) Var áður alltaf að fá eyrnabólgu ...... ❏ b) Var alltaf að fá sýklalyf...... ❏ c) Var með vökva í eyrum...... ❏ d) Heyrði illa ...... ❏ e) Svaf illa ...... ❏ f) Var alltaf með kvef og hor ...... ❏ g) Lækirinn taldið þetta ráðlegt ...... ❏ h) Vegna ráðlegginga frá vinum og kunningjum... ❏ i) Aðrar ástæður:______

Skánaði barninu eftir röraísetningu?

Já ❏ Nei ❏ Veit ekki ❏

Ef já hvað skánaði?: ______144 Telurðu vera einhverjar sérstakar skýringar á því að barnið þitt var „eyrnabarn“ (t.d.)

Í ættinni? Já ❏ Nei ❏

Rysjótt veðurfar? Já ❏ Nei ❏

Reykingar á heimilinu? Já ❏ Nei ❏

Annað: ______

Takk fyrir 145

Paper V. Arason et al. MDR 2006 ERRATUM PAGE 173

TABLE 3. UNIVARIATE ANALYSIS ON DIFFERENT VARIABLES FOR CHILDREN CARRYING PNSP COMPARED TO CHILDREN CARRYING PENICILLIN SUSCEPTIBLE PNEUMOCOCCI.

Penicillin Penicillin Number Variable susceptible non-susceptible P value children pneumococci pneumococci Residence Area H 258 134 20 0.280 Area V 301 199 15 Area E 207 108 12 Area B 58 34 3 Age Mean 4.16 Mean 3.78 (95%CI 4.01-4.30) (95%CI 3.03-4.25) Sex Male 430 249 29 0.462 Female 394 226 21 Number of Mean1.40 Mean 1.63 siblings. (95%CI 1.30-1.50) (95%CI 1.31-1.95) Daycare Yes 752 443 46 attendance No 70 31 4 0.764 Smoking in the Yes 148 94 6 household. No 671 378 44 0.255 Tympanostomy Yes 279 169 20 tubes any time. No 538 301 30 0.766 Tympanostomy Yes 111 70 10 tubes at No 689 391 37 0.175 sampling time. Number of Mean 0.95 Mean 1.78 <0.001 antimicrobial (95%CI 0.82-1.09) (95%CI 1.24-2.32) (AM)courses last 12 months. Number of Mean 21.50 Mean 10.82 <0.001 weeks from last (95%CI 19.46-23.53) (95%CI 7.58-14.06) AM treatment. Prophylactic Yes 12 2 AM No 460 48 0.635 last 12 months. Type of last AM Amoxicillin 105 52 (25.9%) 12 (34.3%) 0.938 Amox.-clav.acid 87 49 (24.4%) 13 (37.1%) 0.144 Fenox.m.pc. 32 15 (7.5%) 1 (2.9%) 0.478 Trimethophrim- 23 14 (7.0%) 1 (2.9%) 0.705 sulpha Erythromycin 20 13 (6.5%) 0 Azithromycin 71 41 (20.4%) 6 (17.1%) 0.820 Cefuroxime 6 5 (2.5%) 0 Cefalexin 9 5 (2.5%) 1 (2.9%) 1.000 Dicloxacillin 8 7 (3.5%) 1 (2.9%) 1.000