., ORIGINAL ARTICLES
We would like to thank the following people for their kind LABORATORY SURV~ILLAN.CEOF assistance: the staff at Red Cross War Memorial Children's Hospital and at City Hospital for Infectious Diseases, Mr 5 Moeti, Ms A van SWGELLA DYSENTERIAE TYPE 1 IN Eck, Mr J Otto, Dr H VISSer, Ms V Dekenah, Ms M Naidoo, Or R Marshall, Dr D Bass, Mr R Sayed, Professor M L Thornpson and the KwAZuLU-NATAL parents and guardians of the children who participated in the study. The Medical Research Council is thanked for financial J A Karas, DG Pillay, T Naicker,A W Sturm support.
References Objective. To collect data on the antimicrobial susceptibility of 1. Ferrinho e Buch E, Reinach SG. Mortality due to meningococcal infection in South Africa, 1968 -1986. S Afr I Epidemiol Infrd 1993; 8(2): 52-54. Shigella dysenteriae type 1 in KwaZulu-Natal, including the 2. Department of National Health and Population Development (DNHPD). Notifiable Medical Conditions. Epidemio/ogi-17. 4. DNHPD. Meningococcal infection. Epidemio/ogi-21. ability of laboratories to participate in a provincial 5. Donald PR. Bwger PJ, Van Zyl LE. Meningococcal disease at Tygerberg Hospital. S Afr Med I 1981; 6lk m-27S. surveillance programme. 6. Po_ PC, Donald PR. Moodie I, Slater C, Kibe.l MA. Meningitis in Cape Town children. S Afr Med I 1984; 66: 7:'8-763. Design. Prospective descriptive study. 7. Rydec PC, Beally DW, de V Heese H. Group B meningococcal infection in children during an epidemic in Cape Town, South Africa Ann Trap Paediatr 1987; 7: 47-53. Setting. Hospital laboratories in KwaZuhi-Natal, including 8. Frasch CE, Coetzee Gl, ZahradniJ<)M, Feldman HA, Koomhof HJ. De~elopment and evaluation of a group B serotype 2 protein vaccine: report of a group B field trial Med Trop peripheral laboratories and the medical microbiology 1983; 43: 177-183. laboratory of the University of Natal. 9. Zollinger WO, Boslego l, Morgan E, et aL Meningococcal serogroup B vaccine protection trial and follow-up studies in Chile. NIPH Ann 1991; 1'" 211-213. 10. Bjune C, Hiby EA, Gronnesby jK, Arnesen D. Effect of an outer membrane vesicle vaccine Main outcome measures. Antimicrobial susceptIbility pattern of against serogroup B meningococcal disease in Norway. Lln Accepted 13 Aug 1998. -.----ORIGINAL ARTICLES An outbreak of Shigella dysenteriae type 1 infection has been and loracarbef 30 pg. Extended-spectrum ~lactamasetesting 1 3 ongoing in KwaZulu-Natal since the beginning of 1994. - This was performed using a double disc diffusion method.10 During pathogen, which is the major cause of epidemic dysentery in the study period a selection of consecutive isolates from King Africa, appears to have spread southwards to South Africa Edward VIII Hospital were included for susceptibility testing. from other parts of Africa, namely Zaire, Burundi, Zambia, A quality-eontrol survey was conducted on a random Zimbabwe and Mozambique, where large epidemics have been selection of laboratories to determine their ability to culture reported since the 1980s!.s S. dysenteriae type 1 causes a stool samples for S. dysenteriae type 1 and Shigella flexneri. Three spectrum of disease ranging from mild watery diarrhoea to freeze-dried quality-eontrol specimens were prepared dysentery, haemorrhagic colitis and toxic megacolon, and is containing equal volumes of a McFarland 1.0 stand~d associated with haemolytic uraemic syndrome (HUS).6 The suspension of Proteus mirabilis and non-pathogenic Escherichia severity of infection of this serotype as opposed to other coli. The first specimen also had S. dysenteriae type 1, the second Shigella is thought to be due to the production of a potent S. flexneri and the third no pathogen. Laboratories were neur~o-enterotoxinknown as Shiga toxin.7 It is also multiply requested to isolate and perform antibiotic susceptibility testing resistant to antibiotics such as ampicillin, co-trimoxazole, on clinically significant organisms. The following antibiotic tetracycline and chloramphenicol. Of particular concern is the susceptibilities were to be determined: ampicillin, tetracycline, emerging resistance to quinolone antimicrobials such as chloramphenicol, co-trimoxazole, cefuroxime, cefotaxime, co nalidixic acid, with resistance as high as 57% in Burundi in amoxiclav, gentamicin, nalidixic acid and ciprofloxacin. An 1994.8 error in susceptibility was defined as reporting a resistant Following the isolation of a nalidixic acid-resistant S. strain susceptible, or reporting a susceptible strain resistant. dysenteriae type 1 strain in KwaZulu-Natal· we decided to All data were captured and analysed using EpiInfo version 6 undertake a laboratory surveillance programme in order to software (Centers for Disease Control, USA). determine the susceptibility pattern of the organism in our province. S. dysenteriae type 1 is not an organism that is easy to isolate from stools, and many epidemics in Africa have been RESULTS misidentified as being of amoebic or viral causation! We A total of 521 isolates on nutrient agar slopes and sealed agar therefore also conducted a quality-i:ontrol survey of plates of varying quality were received. Of these 322 (61.8%) laboratories in the province to determine their ability to culture were confirmed to be S. dysenteriae type 1. Of the remaining S. dysenteriae type 1. cultures 5 (0.9%) yielded S. flexneri, 40 (7.8%) other Enterobacteriaceae, and 2 (0.4%) Gram-positive organisms; 152 (29.2%) had no growth. MATERIAL AND METHODS The source of S. dysenteriae type 1 isolates is depicted in An instruction was issued in December 1994 through the Fig. 1. Thirty-five of the isolates received were unlabelled as to provincial laboratory services of KwaZulu-Natal to all their origin. For the susceptibility testing we included 32 laboratories in the province to send isolates of S. dysenteriae isolates that had been isolated in our laboratory from patients type 1 to the medical microbiology laboratory of the University presenting at King Edward VIII Hospital. The susceptibility of Natal, Durban. Transport instructions were that they were to pattern was determined in all 354 of the isolates, and was be sent on nutrient or equivalent agar slopes via routine similar with only 6 exceptions (Table I). Three strains (0.8%), transport channels. All isolates were stored on these slopes at 4 - 8°C until further testing. Data were recorded on the date of Number of isoIaIes isolation, and the laboratory that had done the isolation was 100 ,------, also recorded. Stored isolates were sub-i:ultured onto xylose/lysine/ 80 deoxycholate agar (Oxoid, UK) and were confirmed as being 60 54 S. dysenteriae type 1 by a negative catalase test, biochemical tests (glucose, mannitol, indole) and serotyping with type 1 40 specific antisera (Sanofi-Pasteur, France). Susceptibility testing 20 was performed using the Kirby-Bauer disc diffusion method 10 10 9 5 (National Committee for Clinical Laboratory Standards, 0 ID ~ m "ID CIJ CIJ Cl :D m Z c: Villanova, USA) for the following antibiotics and disc 3 iD l? e. "0 g S- ~ ::> S- ~ ,5 0 ;:r. 5 e. CT e. .,- '" :lE e. 0 e.t c: ~ 9 :lE strengths: ampicillin 10 pg, co-trimoxazole 15 pg, tetracycline 0 oil §: .. .. '" a f ..::> ::> .. ::> ~ S- ;:r .. 30 pg, chloramphenicol 30 pg, nalidixic acid 30 pg, .. ~ Hospitals ciprofloxacin 5 pg, ofloxacin 5 pg, ceftriaxone 30 pg, azithromycin 15 pg, fosfomycin 200 pg, pivrnecillinam 10 pg Fig. 1. Source ofisolates - S. dysenteruie type 1 isolates received from hospital laboratories in KwaZulu-Natal (N = 322). January 1999, Vo!. 89, No. 1 SAMJ ORIGINAL ARTICLES susceptibility results is shown in Table ll. Analysis was difficul Table L Antibiotic susceptibility of S. dysenteriae type 1 strains all collected over the study period (N= 354) as only 2 of the laboratories had the available discs. There were no errors for these 2 laboratories. XLD medium was Susceptible available in 24 laboratories (82.8%), and OCA medium in 4 No. Antibiotic % (13.7%). One laboratory had both of these media and 2 Ampicillin 0 0 laboratories had neither. In addition 5 laboratories (17.2%) usec Co-trimoxazole 3 0.8 Salmonella-Shigella medium. This included the 2 laboratories Tetracycline 0 0 that had neither XLD nor OCA medium. Antisera for diagnosll Chloramphenicol 0 0 of were available in 26 laboratories (89.7%). Nalidixic acid 351 99 Shigella Gprofloxacin 354 100 Ofloxacin 354 100 Pivmecillinam 354 100 DISCUSSION Ceftriaxone 354 100 . A large number of isolates were analysed over the study periD< Azithromycin 354 100 and the majority were confirmed to be S. dysenteriae type 1. Thl Fosfomycin 354 100 large number of no-growths among the specimens received car Loracarbef 354 100 probably be attributed to lack of appropriate transport resources; isolates were not always timeously and correctly transported. Some isolates were sent under conditions that 1 each from Empangeni, King Edward VIII and Addington would not ensure survival of the organism, whereas the initial hospitals, were found to be resistant to nalidixic acid. Three recommendations for transporting the specimens would have isolates were found to be susceptible to co-trimoxazole, 2 from kept the isolates viable for prolonged periods. King Edward VIII and 1 from Eshowe Hospital. All isolates Surveillance isolates were received from only 11 laboratories. were found to be resistant to ampicillin, tetracycline and Reasons for other laboratories not sending isolates despite chloramphenicol, and all isolates were found to be susceptible being situated in the epidemic region could include failure to to ceftriaxone, ciprofloxacin, ofloxacin, pivmecillinam, isolate the organism owing to use of incorrect media and lack azithromycin, loracarbef and fosfomycin. Extended-spectrum of proper training in isolating pathogens from stool, lack of ~lactamaseproduction was not detected in any of the isolates. transport for isolates to our laboratory and lack of motivation. Of the 29 laboratories surveyed, 23 (79%) were able to isolate Four of the laboratories from which isolates were received and identify Shigella to the genus level, and 18 (62.1%) and 21 were able to isolate more than 30 strains over the study period. (72.4%) were able to identify S. dysenteriae and S. jlexneri to the These laboratories were from different regions; some were species level respectively. The full identification to serotype of isolated rural hospital laboratories such as Benedictine S. dysenteriae type 1 was made by 9 laboratories (31%). Non (Nongoma), Bethesda (Ubombo) and Eshowe, and one was a pathogenic species were reported as pathogens in 13 (44.8%) tertiary care institution, namely Addington Hospital (Durban). S. dysenteriae type 1 samples, 12 (41.3%) S. flexneri samples and It seems, therefore, that individual factors influenced whether 14 (48.3%) pathogen-free samples. A summary of the laboratories were able to isolate the organism and whether the) would participate in a surveillance programme. Education of laboratory staff regarding their responsibility in playing a Table D. Quality-eontrol specimens - susceptibility testing of s. greater role in public health by detecting and monitoring dYse1lteriae type 1 (N= 18) . outbreaks of infectious diseases needs to be addressed. Number of laboratories with: Nalidixic acid is a quinolone antimicrobial agent and is the Error: mainstay of therapy for epidemic multidrug-resistant Shigella resistant dysentery. Resistance to this drug has been detected in S. Discs Error: susceptible called dysenteriae type 1 outbreaks in Africa" and Asia." The low level called resistant susceptible available of resistance detected in our study is consistent with that 1 Ampicillin 18 N/A described in Zimbabwe.U Tetracycline 15 N/A o Although nalidixic acid resistance does not appear to be a Chloramphenicol 17 N/A o problem at present this situation could change rapidly, as was Co-trimoxazole 16 N/A o Nalidixic acid 9 o N/A the case in Burundi (A. Ries - unpublished data). The Ciprofloxacin 6 o N/A mechanism of the rapid dissemination of resistance to nalidixic Cefuroxime 16 o N/A acid is not clear. Nalidixic acid resistance is a consequence of a Cefotaxime 16 o N/A change in the Shigella topoisomerase IV target site that results Gentamicin 16 o N/A from a chromosomal change of the gyrA gene.13 Plasmid Co-amoxiclav 16 9 N/A mediated resistance, which may result in rapid spread of ~ ~.. ORIGINAL ARTICLES ------•------ resistance, has not been detected for nalidixic acid; however, a that results of different laboratories can be compared and plasmid designated pYDl, conferring trimethoprim resistance, antibiotics that are part of the essential drugs list can be has been shown to increase the frequency of mutation to included. It is most likely that susceptible strains are reported nalidixic acid resistance in recipient strains." It is possible that as being resistant for co-amoxiclav because of deterioration of the dissemination of this plasmid may contribute to the spread discs due to clavulanic acid being hygroscopic. of nalidixic acid resistance by inducing mutations in different In view of increasing budgetary constraints and the expertise strains of S. dysentenae type 1. It is essential that we continue to required and costs involved in performing accurate stool monitor susceptibility of Shigella to nalidixic acid and to other cultures, it would seem that the best possible solution would be agents that are also being used in the therapy of S. dysenteriae to perform stool cultures at certain sentinel sites only. ptese type 1 infections, namely ceftriaxone and ciprofloxacin. sentinel sites should have properly trained staff and be fully The search for new antibiotics to treat shigellosis is important equipped, and could form part of an infectious diseases in the wake of its rapidly emerging resistance to present survei.lliince network. This would provide more accurate l5 I agents. • • Among the newer antibiotics we tested, azithromycin information than having sub-standard cultures performed at all has already been used in a clinical trial17 and was found to be hospital laboratories. The information obtained from such as good as a fluoroquinolone. Others such as fosfomycin have sentinel sites would be more useful for epidemic control, and been used in the treatment of cases of E. coli 0157 infection, would give clinicians more accurate information regarding such as in the recent epidemic in Japan (T. Takeda et aI. antimicrobial susceptibility and the nature of the causative unpublished data) while loracarbef still needs to be evaluated. pathogen than the current system. Extended spectrum ~lactamaseproduction among It is clear from this report that KwaZulu-Natallacks an Enterobacteriaceae exists in our hospital and throughout adequate public health laboratory programme to monitor and KwaZulu-Natal (unpublished data). Owing to the widespread detect infectious diseases. It is likely that this is also the case in use of ceftriaxone and cefotaxime for the treatment of patients many of the other provinces. The cost that KwaZulu-Natal has with severe dysentery in KwaZulu-Natal, we were concerned paid during this epidemic is enormous. It has been estimated that resistance to third-generation cephalosporins might that for every dysentery case presenting at a hospital, there are emerge. However, we did not detect any extended spectrum ~ between 27 and 54 cases in the community.lB The KwaZulu lactamase production among the isolates. Unlike other Natal Shigella epidemic control team's sentinel site surveillance developing countries, South Africa has been able to afford the datal9 show that there are approximately 500 cases of bloody use of third-generation cephalosporins for the treatment of diarrhoea a month at the 10 sentinel sites, which suggests that dysentery. Selective pressure with heavy use of these there could be as many as 15 000 cases of dysentery a month in antimicrobial agents may result in cephalosporin resistance in the sentinel site areas alone. Hospital mortality is estimated to S. dysentenae type 1, which is quite likely to emerge in this be between 5% and 13%.'-' country. The S. dysenteriae type 1 outbreak in KwaZulu-Natal has The quality-eontrol survey indicates that problems exist in been the largest dysentery outbreak in South Africa to date. It the quality of stool cultures in KwaZulu-Natal as only 79% of is apparent that the epidemic is now spreading to other laboratories were able to isolate Shigella from the samples. provinces such as the Eastern Cape and Western Cape There was also a high rate of reporting of non-pathogens, (personal communication - Dr S Oliver, Department of which indicates lack of training as regards interpretation of Medical Microbiology, University of Cape Town). stool cultures. Considering the high inoculum of Shigel/jl in the Laboratory services in our country are currently undergoing quality control samples, none of the laboratories should have a reconstruction process and there is a need for a reference had a negative culture result, suggesting that there is room for laboratory service that would lend itself to playing a greater improvement in a province where Shigella infections are role in public health. endemic. XLD and DCA agar are considered to be the best We recommend that nalidixic acid remain the antibiotic of isolation media for the isolation of Shigella. Only 2 laboratories choice for bacillary dysentery in our region and that the did not have either XLD"Or DCA medium and close to 90% had restructuring of laboratory services include a national appropriate antisera, indicating that the reasons for missing infectious disease surveillance system. Shigella are most likely incorrect media preparation or storage (important factors for both XLD and OCA), or inability of We gratefully acknowledge all the laboratories that took part in technologists to recognise possible Shigella colonies. When this study, the KwaZulu-Natal Shigella Epidemic Control Team, analysing the results of the susceptibility testing it was obvious and Mr Anch-e deKok at Addington Hospital for assisting with the quality control survey. that there was a shortage of antibiotic discs for performing appropriate susceptibility testing, and that there was References considerable variation between laboratories where antibiotics 1. Rollins NC, Wittenberg DF, Coovadia HM, Pillay DC, KaIas lA. Stwm AW. Epidemic Shigdla wereJested. Susceptibility testing should be standardised so dysmleriae type 1 in Natal 1Trop PtdiDtT 1995; 4], 281-284. January 1999, Vo!. 89, No. 1 SAMJ