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 sour- ces 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.