Microbiologic characteristics of exfoliative toxin-producing Staphylococcus aureus.

Exfoliative toxin (ET) production, phage types and antibiotic susceptibilities of 74 strains of Staphylococcus aureus isolated from patients with generalized staphylococcal scalded skin syndrome or bullous impetigo were studied. Of 74 staphylococcal isolates, 61 strains were found to produce ET by the newborn mouse assay method and the latex agglutination method. Fifteen strains were positive for ET-A, 32 for ET-B and 14 for both ET-A and ET-B. Among 61 ET-producing strains 27 (44%) were classified as Phage Group II, 16 (26%) as Group III, and 14 (23%) as Groups I and III. Of 27 Phage Group II strains 14 produced ET-A and 13 produced both ET-A and ET-B, but no strain was positive solely for ET-B. On the other hand 15 of 16 Phage Group III strains and all 14 Phage Group I and III strains produced only ET-B. It was demonstrated that the phage types of staphylococci were closely related to ET types. Characteristically the minimal inhibitory concentrations of penicillin G against ET-producing strains were less than 2 micrograms/ml, in contrast to other pathogenic staphylococci, 60 to 70% of which are highly penicillin G-resistant.