Nasal, axillary, and perineal carriage of Staphylococcus aureus among women: identification of strains producing epidermolytic toxin

Following two outbreaks of staphylococcal scalded skin syndrome in a maternity unit, 500 pregnant women attending an antenatal clinic were screened for carriage of epidermolytic toxin producing Staphylococcus aureus. Nasal, axillary, and perineal swabs were collected from women whose gestational ages ranged from 12-40 weeks. Isolates of S aureus were purified, phage typed, and tested for methicillin sensitivity and production of epidermolytic toxin. The results showed that 164 (33%) women carried S aureus; of these, 100 (61%) were from the nose and three (2%) from axillae, but 41 (25%) strains were isolated from the perineum alone. Screening for nasal carriage alone will therefore miss 25% of carriers. More than one strain of S aureus was identified in seven of 20 women with multiple site carriage. Three (2%) methicillin resistant strains were isolated during the survey, and five (3%) isolates produced epidermolytic toxin. Phage typing identified 63 (34%) strains as non-typable, but 50% of isolates typed either groups I, II or III, and a further 10% represented varying combinations of these and other phage groups. These results provide baseline information on S aureus in the community, and identification of methicillin resistant and toxin producing strains shows a reservoir of outbreak potential which could become relevant on hospital admission of such a carrier.