Nasal, Axillary, and Perineal Carriage of Staphylococcus Aureus Among

J Clin Pathol 1991;44:681-684 681 Nasal, axillary, and perineal carriage of aureus among women:

Staphylococcus J Clin Pathol: first published as 10.1136/jcp.44.8.681 on 1 August 1991. Downloaded from Identification of strains producing epidermolytic toxin

S J Dancer, W C Noble

Abstract by which the mother may also become infec- Following two outbreaks of staphylococ- ted, leading to the development of a breast cal scalded skin syndrome in a maternity abscess. '0 unit, 500 pregnant women attending an S aureus of certain phage groups tend to be antenatal clinic were screened for car- associated with particular skin diseases." A riage of epidermolytic toxin producing rare neonatal disease called the staphylococcal Staphylococcus aureus. Nasal, axillary, scalded skin syndrome and the related milder, and perineal swabs were collected from but more common form, pemphigus neo- women whose gestational ages ranged natorum, are generally caused by strains from 12-40 weeks. Isolates of S aureus belonging to phage group H1."2 3 Both these were purified, phage typed, and tested for conditions fall within a continuous spectrum methicillin sensitivity and production of which ranges from localised bullous impetigo epidermolytic toxin. The results showed to a generalised epidermolysis of the skin that 164 (33%) women carried S aureus; resembling widespread first degree burns.'4 of these, 100 (61%) were from the nose The causative strain of S aureus colonising and three (2%) from axillae, but 41 sites such as nose or umbilical stump in neo- (25%) strains were isolated from the nates"5 produces epidermolytic toxins which perineum alone. Screening for nasal are absorbed and eventually lead to separation carriage alone will therefore miss 25% of of cells within the stratum granulosum of the carriers. More than one strain of S epidermis.'6 Toxin producing strains are iden- aureus was identified in seven of 20 tified by wrinkling or peeling of the skin women with multiple site carriage. (Nikolsky sign) in neonatal or hairless mice Three (2%) methicillin resistant strains following subcutaneous inoculation of suspec-

were isolated during the survey, and five ted isolates.'3 '7 http://jcp.bmj.com/ (3%) isolates produced epidermolytic At least two epidemics of staphylococcal toxin. Phage typing identified 63 (34%) scalded skin syndrome have occurred in a strains as non-typable, but 50% of London hospital maternity unit in consecutive isolates typed either groups I, II or III, years, the first affecting 12 babies,'8 the second and a further 10% represented varying more than 80 neonates.'0 Two sporadic cases combinations of these and other phage and a mini outbreak affecting four babies and

groups. an adult have been identified more recently, all on September 30, 2021 by guest. Protected copyright. These results provide baseline infor- strains typed group II and produced a positive mation on S aureus in the community, Nikolsky sign in the mouse bioassay. and identification of methicillin resistant The common appearance of this otherwise and toxin producing strains shows a rare condition in our matemity unit prompted reservoir of outbreak potential which us to question the incidence of epidermolytic could become relevant on hospital toxin producing staphylococci in the com- admission of such a carrier. munity. Epidemiological studies reporting the prevalence of toxin producing strains have generally examined isolates from clinical sources such as hospital patients or patients with Nasal carriage of Staphylococcus aureus in nor- superficial skin lesions2"2' but not from normal mal populations is about 35% in both sexes,' subjects. Immunological studies show that Division of Microbiology and but this may vary according to age2 and race.3 more than 50% of those over 10 years of Institute of A carrier may be unaware of the potential age possess antitoxin and 80% of cord blood Dermatology, United pathogenicity of the bacteria that they specimens contain epidermolytic toxin anti- Medical and Dental harbour, both to themselves and Schools, St Thomas's others.' body,24 which suggests that toxigenic strains Hospital, London Newbom babies are particularly at risk from certainly exist outside hospital but that the S J Dancer, W C Noble S aureus carried by mothers or attendant true prevalence remains obscure. Correspondence to: medical staff because of an immature immune Similarly, the prevalence of different phage Dr S J Dancer, system and the Department of Medical increased prevalence of S groups in the community is not well estab- Microbiology, aureus in hospitals.2 Nasal carriage of lished. Groups I and II strains are said to St Bartholomew's Hospital, infants on discharge from hospital approached West Smithfield, London colonise about 30 and 25%, respectively, of ECIA 7BE 100% in a staphylococcal epidemic but is normal nasal carriers, while group III strains Accepted for publication more usually about 60%.' Colonisation or account for only 15% of carriers.' Phage 25 March 1991 infection of the newborn is the principal route group II staphylococci accounted for 8-2% of 682 Dancer, Noble

2969 isolates sent to the Division of Hospital ANTIBIOTIC SENSITIVITY TESTING Infection (CPHL) over a period of three mon- Antibiotic sensitivity was tested by means of ths in 1986. Forty one (7%) of 584 nasal Oxoid "multo-disks" containing penicillin

isolates sent during 1987-1988 were group II, "G" 1 5 IU, tetracycline 10 ,ug, erythromycin J Clin Pathol: first published as 10.1136/jcp.44.8.681 on 1 August 1991. Downloaded from but these were also from all sources, most 5 4g, clindamycin 2 pg, gentamicin 10 pg and being long term hospital inpatients (Marples neomycin 10 pg. Tests were performed at 37°C RR, personal communication). on Diagnostic Sensitivity Test Agar (Tissue It was thus relevant to carry out a survey Culture Services). on a group of pregnant women living outside the hospital environment by examining nasal, METHICILLIN SENSITIVITY TESTING axillary, and perineal sites for staphylococcal Mueller-Hinton agar was flooded with a heavy carriage. The results would contribute to- inoculum and incubated at 34-35°C for 24 and wards present knowledge of carrier rates in 48 hours. If the zone around the methicillin the general population because no difference in disc was less or equal to 13 mm the test was carriage is attributable to sex.2928 Further repeated using oxacillin 1 pg (OX1), methi- useful epidemiological information would be cillin 5 pg (MT5), and amoxycillin 2 pg obtained from an at risk group on carriage (AML2) discs. Zone sizes were measured in the site, prevalence of antibiotic resistance, and order OX1:MT5:AML2. different phage groups. DETECTION OF EPIDERMOLYTIC ACTIVITY Methods Adult hairless mice were inoculated subcutan- Five hundred women attending routine ante- eously with about 105 CFU staphylococci in natal outpatient clinics were chosen at random 0-2 ml nutrient broth. A positive Nikolsky sign to donate nasal, axillary, and perineal swabs. (wrinkling or peeling of the skin) was recorded Gestational ages ranged from 12 weeks (book- two to four hours later in strains considered to ing) to 40 weeks (term) and permission was have epidermolytic activity.'3 17 obtained from the mothers before swabbing took place. Three consultant clinics were Results visited weekly on a rotational basis over a GENERAL CARRIER RATE AND SITE OF CARRIAGE period of three months; timing of visits was It was found that 164 (33%) women carried S varied to avoid subject duplication and also to aureus; 100 (20%) carried strains in the nose, minimise the risk of collecting one strain of three (0-6%) in the axillae and 41 (8-2%) in the S aureus transferred between a social group. perineum (fig 1). Sixteen (3-2%) women carried These women were healthy, aged 17-42 years, S aureus in the nose and perineum, two (0 4%) from all social classes, and had no medical in the nose and axillae, and in a further two histories of note. They did not work in hospi- (0 4%) carriage was evident in all three sites. tals or have any antenatal problems necessitat- More than one strain of S aureus was identified

ing previous hospital admission or outpatient in seven of 20 women with multiple site http://jcp.bmj.com/ appointments other than the normal routine carriage. antenatal checkups. Brief questioning about One of two subjects in whom S aureus was partners' occupation and place of work helped confirmed from all three sites produced the to confirm eligibility for the survey, as subjects same strain (as shown by phage typing), but with indirect association with the hospital three different strains were obtained from the environment were excluded. other. There were no cases in whom two or

more different strains were isolated from the on September 30, 2021 by guest. Protected copyright. SWABBING PROCEDURE same anatomical site. Standard swabs were taken from three sites of potential carriage. It was regarded as sufficient PHAGE TYPING to sample no more than the first centimetre of One hundred and eighty four strains were sent nasal epithelium when swabbing the nose,' and for phage typing and results were taken from perineal swabs were taken by medical staff reactions at routine test dilution. Sixty three during abdominal examination. Swabs were (34%) strains were non-typable; 27 (15%) placed in transport medium and inoculated on typed group I, 25 (14%) group II, and 36 agar within six to 24 hours. (20%) group II (fig 2). Eight (4%) strains reacted with phage 95, and eight (4%) each ISOLATION OF S aureus typed groups I, III (95) and groups I and III. Swabs were inoculated on to horse blood agar, There were five (3%) group V reactions and two incubated at 37°C for 24 hours. An aztreonam (1%) group I and II reactions. One isolate disc (30 pg; Oxoid) was placed on each Non-typable ro:u* 111 (209%) (34%) inoculum to aid purification. S aureus was Group I (15%) Group 11 (14%) identified 9 by colony morphology, pigment Phage14-:5 production, and slide agglutination techniques Groups 1,111,95 (4%) Groups 1,111 (4%) ("Staphaurex" rapid latex test kit; Wellcome). roup V (3%) roups I,ll (1%) Dubious colonies were further subjected to Groups I,V (0-5%) tube coagulase testing. Purified isolates were Phage 81 (0-5%) phage typed at the Central Public Health MRSA (2%) Laboratory using the International Basic Set of E Epidermolytic toxin producing S aureus (3%) test Strains typing phages at routine dilution. Figure 1 Distribution of bacteriophage groups, MRSA, were stored in glycerol broth on glass beads at and epidermolytic toxin producing strains among -70°C. S aureus isolatesfrom antenatal women. S aureus carriage in pregnant women 683

Figure 2 Proportion of Staphylococcal carriage (33%) women attending an antenatal clinic staphylococcal carriers presented no difficulty because sampling was accepted as among 500 antenatal Nose, axilla, 0Dn-staphylococcal women and distribution of perineum (0-4%)I11-1 ' carriage (67%) part of the normal routine and the mothers to S aureus among nasal, be welcomed prior bacteriological screening. J Clin Pathol: first published as 10.1136/jcp.44.8.681 on 1 August 1991. Downloaded from axillary, andperineum Perineum (8 2%)_- carriage sites. More theoretical explanations for the higher Nose and axilla- rate of perineal carriage could, perhaps, be (0-4%) attributable to pregnancy: it has been reported that there is a dramatic rise in the number of "I Nose (20%6) staphylococci in the vaginal vestibule of sows 12 hours before giving birth.3' It is also known from human studies of vaginal and Axilla (0-6%) Nose and perineum (3-2%) vulval flora that shortly before delivery the vaginal flora consists mainly of coagulase (0 5%) showed a group I and V combination negative staphylococci and there is therefore a and one (0-5%) reacted-solely with phage 81. A predominance ofthese organisms on the skin of single strain found in all three sites typed group the newborn baby.3' II (55, 71) and three strains from one subject When the results from 30 women newly typed III (47, 53, 54, 84, 85), group I (79), and admitted to the labour ward were examined it non-typable. was found that nine (30%) carried S aureus, and in only one of these was carriage perineal. ANTIBIOTIC RESISTANCE PATTERNS These women were included in the survey. If Antibiotic sensitivity testing showed that 57% this high figure for perineal carriage is accepted ofstrains were resistant to penicillin; 25% were nasal screening of a suspect population during fully sensitive to all antibiotics tested; 10% an outbreak would miss one in four staphylo- strains were resistant to both penicillin and coccal carriers. The observation that perineal tetracycline, 3% resistant to penicillin and carriage assists more readily in the dispersal of erythromycin, and 2% resistant to tetracycline the organism also becomes more relevant.29 alone. One strain was resistant to penicillin, The heightened metabolic rate seen in preg- gentamicin, and neomycin, one resistant solely nancy, leading to increased activity of eccrine to erythromycin, and one was resistant to and apocrine glands, may also enhance staphy- penicillin, tetracycline, and neomycin. lococcal carriage as S aureus is found principally in sites bearing these glands. ' The METHICILLIN RESISTANCE AND EPIDERMOLYTIC incidence of axillary carriage was just 2%, TOXIN PRODUCTION however and overall percentage of carriage fell Three (less than 2%) strains were methicillin within normal limits (33%). Deodorant use resistant; two were non-typable, and the third mentioned by subjects at the time of swabbing resembled EMRSA-2 typing group I (80). Five probably did not affect carriage rate either.32

(3%) strains produced epidermolytic toxin as Twenty (12%) staphylococcal carriers were http://jcp.bmj.com/ identified by the mouse bioassay. One typed multiple site carriers; of these, seven (4%) group II (3A, 3C, 55, 71), three were non- carried different strains of S aureus. Solberg typable, and the fifth typed group I and III (29, found that more than one strain was carried by 52, 52A, 80, 47, 53, 75, 83A, 84). staphylococcal carriers on 10% of occasions.29 Isolation of more than one strain may reflect sporadic or intermittent carriage before a resi-

Discussion dent strain becomes established.33 No more on September 30, 2021 by guest. Protected copyright. This survey was undertaken principally than one strain from an anatomical site was because of the occurrence of two outbreaks of found during this survey; this does not exclude an otherwise rare disease, the staphylococcal coexistence of discrete minority populations, scalded skin syndrome, within a two year but it does support the finding that an avirulent period.'8 '" Speculation on the cause of these strain may be planted in a carrier site to prevent epidemics led us to question the incidence of colonisation by a potentially more pathogenic epidermolytic toxin producing staphylococci in organism. the community, because only hospital or clini- Phage typing results mirror the findings of a cal isolates have been screened for production study by Ramamurti and Kanz, who reported of epidermolytic toxin.2023 that environmental strains from schools and The overall carriage rate for S aureus (33%) sports facilities were 15% group I, 13% group is consistent with many reports on staphylo- II, 23% group III, and the rest, nearly half, coccal carriage.' The high perineal carriage rate non-typable.35 (25% carriers), however, does not agree with Other reports differ in the proportions quoted previous findings for example, Polakoff et al for example, group I 30%, group II 25%, reported 13% perineal carriage among 361 group III 15% and the rest lysed by phages anaesthetised patients,27 and Solberg produced 42D, 81 or 187 or non-typable.' We were a similar result from 2014 patients screened on principally interested in the incidence of group admission to hospital.29 Black recorded rates of II strains, because of their association with the 19 and 21% for female and male perineal staphylococcal scalded skin syndrome. Our carriage, respectively.25 The diverse results results showed that pregnant women attending obtained from these and other studies may have an antenatal clinic provided 14% group II been due in part to the difficulty in obtaining strains, nearly twice the figures quoted from adequate perineal swabs from normal subjects. CPHL (8-2% and 7%) (Marple RR, personal In this survey perineal swabbing of pregnant communication). 684 Dancer, Noble

The identification of methicillin resistant 8 Hargiss C, Larson E. The epidemiology of Staphylococcus aureus in a newborn nursery from 1970 through 1976. (MRSA) and epidermolytic toxin producing Pediatrics 1978;61:348-53. strains from the survey established the exist- 9 Noble WC, Williams REO, Jevons MP, Shooter RA. Some aspects of the nasal carriage of staphylococci. J Clin Pathol ence of a reservoir of potentially pathogenic 1964;17:79-83. J Clin Pathol: first published as 10.1136/jcp.44.8.681 on 1 August 1991. Downloaded from staphylococci in the community especially as 10 Williams REO, Blowers R, Garrod LP, Shooter RA. Hos- pital Infection. London: Lloyd Luke, 1960:44-62. one MRSA strain resembled EMRSA-2.36 11 Noble WC, White MI. Staphylococcal skin infection in man. Epidermolytic toxin producing strains were In: Easmon CSF, Adam C, eds. Staphylococci and staphylococcal infections. London: Academic Press, 1983: carried by five women out of the original group 165-91. of 500, or 3% of 184 strains collected. If most 12 Parker MT, Tomlinson AJH, Williams REO. Impetigo contagiosa: the association of certain types of Staphylococ- adults have antibodies to epidermolytic toxins24 cus aureus and of Streptococcus pyogenes with superficial then epidermolytic toxin producing strains skin lesions. J Hyg Camb 1955;53:458-73. 13 Melish ME, Glasgow LA. The staphylococcal scalded skin must be readily transmissible among indi- of syndrome.J Development an experimental model. N viduals in the community. The adult case we Engl Med 1970;282:1114-9. 14 Lyell A. Toxic epidermal necrolysis (the scalded skin identified in the mini outbreak presumably had syndrome). A reappraisal. BrJDermatol 1979;100:69-86. had no prior contact with a toxin producing 15 Wolinsky EP, Lipitz PJ, Mortimer EA, Rammelkamp CH Jr. Acquisition of staphylococci by newborns; direct and strain. indirect transmission. Lancet 1960;ii:620-2. Despite this knowledge our original question 16 Dimond RL, Wolff HH, Braun-Falco 0. The staphylococcal scalded skin syndrome. An experimental histodermato- as to the cause of the outbreaks experienced in logical and electron microscopic study. Br J Dermatol this hospital remains unanswered. There are 1977;96:483-92. 17 Arbuthnott JP, Kent J, Noble WC. The response of hairless probably several factors which contribute to mice to staphylococcal epidermolytic toxin. BrJ Dermatol the initiation and subsequent propagation of an 1973;88:481-5. 18 Dancer SJ, Simmons NA, Poston SM, Noble WC. Outbreak epidemic. For example, individual policies and of staphylococcal scalded skin syndrome among neonates. practices of the hospital concerned, domestic Infect Dis 1988;16:87-103. 19 Dancer SJ, Poston SM, East J, Simmons NA, Noble WC. resources, ward layout, ventilation systems, age An outbreak of pemphigus neonatorum.J Infect Dis 1990; and architecture. It was long ago established 20:73-82. 20 Kapral FA. Staphylococcus aureus: some host-parasite that isolation measures could reduce the rate of interactions. Ann NY Acad Sci 1974;236:267-76. postoperative wound infection,37 and wide- 21 Galinsky J. Exfoliatin production by Staphylococcus aureus of phage group II. In: Jeljaszewicz J, ed. Staphylococci and spread environmental contamination, but not staphylococcal diseases. Stuttgart: Gustav Fischer Verlag, staff carriage, has been a feature in some out- 1976:517-21. 22 de Azevado J, Arbuthnott JP. Prevalence of epidermolytic breaks.38 The susceptibility of a particular toxin in clinical isolates of Staphylococcus aureus. J Med hospital population into which a strain is Microbiol 1981;14:341-4. 23 Piemont Y, Rasoamananjara D, Fouace JM, Bruce T. introduced is also relevant - in this case a Epidemiological investigation of epidermolytic toxin maternity ward containing postpartum women producing Staphylococcus aureus strains in hospital patients.J Clin Microbiol 1984;19:417-20. and newborn babies; but adult cases of 24 Melish ME, Chen F, SprouseS, Stukey M, Murata MS. staphylococcal scalded skin syndrome, though Epidermolytic toxin in staphylococcal infection: toxin levels and host response. In: Jeljaszewicz J, ed. Staphyl- very rare, are most often associated with ococci and staphylococcal infections. Stuttgart: Gustav immune suppression in, for example, renal Fischer Verlag, 1981:287-98. patients.39 Further points include personal 25 Black T. The bacteriological flora of the skin and its relation to post-operative wound infection. Trans Soc Occup Hyg http://jcp.bmj.com/ habits of members of staff and the ability of a 1966;16: 18-23. 26 Noble WC, Valkenburg HA, Wolters CHL. Carriage of carrier to disperse an organism; staff have been Staphylococcus aureus in random samples of a normal implicated in two recent outbreaks in the population.J Hyg Camb 1967;65:567-73. 27 PolakoffS, Richards IDG, Parker MT, Lidwell OM. Nasal United Kingdom"8'0 and in other elsewhere. and skin carriage of Staphylococcus aureus by patients Finally there is the pathogenicity of the strain undergoing surgical operations.J Hyg Camb 1967;65: 559-66. concerned. 28 Noble WC. Skin carriage of the Micrococcaceae.J Clin Pathol 1969;22:249-53. 29 Solberg CO. A studyof carriers of Staphylococcus aureus. on September 30, 2021 by guest. Protected copyright. Acta Med Scand 1965;(Suppl)178: 1-96. We thank the staff and patients of the McNair Centre Maternity 30 Allaker RP, Lloyd DH, Lamport Al. Bacterial interference Unit at Guy's Hospital, without whose cooperation this study in the control of exudative epidermitis of pigs. In: von would not have been completed. TscharnerC, Halliwell REW, eds. Advances in veterinary This study was supported by grants from the special trustees dermatology. London: Bailliere Tindall, 1990:327-34. of Guy's Hospital, and Procter and we are 31 Sarkany I, Gaylarde CC. Bacterial colonization of the skin of Gamble, whom the newborn.J Pathol Bacteriol 1968;95:115-22. grateful. SJD is indebted to these bodies for support. 32 Somerville DA. The normal flora of the skin in different age groups. [Thesis], Univeristy of Otago, New Zealand: 1966. 33 Henning C, Hillborgh U, Lindvall K, et al. Comparison of Staphylococcus aureus carriers and skin infection rates in hospital and office employee.J Hyg Camb 1979;83:437-44. 34 Aly R, Shinefield HR, eds. Bacterial interference. Boca Raton, 1 Noble WC. Microbiology of human skin. London: Lloyd Florida: CRC Press, 1982. Luke, 1981:152-81. 35 Ramamurti DV, Kanz E. The staphylococcus outside hosp- 2 Ayliffe GAJ, Brightwell KM, CollinsBJ, Lowbury EJL, ital. I The occurrence of staphylococcal phage types in the Goonatilake PCL, Etheridge RA. Surveys of hospital extra-hospital environment. Z Bakt Parasitol Infekt Hyg I infection in the Birmingham area. 1. Effect of age, sex, Abt Orig 1972;156:399-405. length of stay and antibiotic use on the nasal carriage of 36 Richardson JF, Marples RR. Another strain of methicillin- tetracycline resistant Staphylococcus aureus and on post- resistant Staphylococcus aureus epidemic in London. operative wound infection. JHyg Camb 1977;79:299-314. Lancet 1988;ii:748-9. 3 Millian SJ,Baldwin JN, Rheins MS, Weiser HH. Studies on 37 Williams REO, Noble WC, Jevons MP, et al. 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Arch Dermatol 1989;125:85-7. 7 Lidwell OM, Brock B, Shooter RA, Cooke EM, Thomas 40 Dowsett EG, Petts DN, Baker SL, et al. Analysis of an GE. Airborne infection in a fully air-conditioned hospital. outbreak of the staphylococcal scalded skin syndrome; IV Airborne dispersal of Staphylococcus aureus and its strategies for typing non-typable staphylococci. J Hosp acquisition by patients. J Hyg Comb 1975;75:445-74. Infect 1984;5:391-7.