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A Retrospective Study of Methicillin-Resistant Staphylococcus aureus Clinical Strains in Tokyo University Hospital

1995; Elsevier BV; Volume: 1; Issue: 1 Linguagem: Inglês

10.1007/bf02347728

1437-7780

Tae Tanaka, Katsuko Okuzumi, Aikichi Iwamoto, Keiichi Hiramatsu,

Bacterial Identification and Susceptibility Testing

Staphylococcus aureus clinical strains isolated in 1982 and 1992 at Tokyo University Hospital were studied for their carriage of mecA gene, antibiotic susceptibility patterns, toxin production, coagulase isotypes, and ribotyping patterns. The mecA-carrying strains in 1982 were mostly producers of type-4 coagulase (21 out of 31;68%), but producers of other coagulase types (type-1,-2,-7) were also found. The degree of methicillin resistance varied but was moderate with these strains (MIC50=16; range, 0.5–512 μg/ml at 32°C with 2% NaCl), and some strains were even judged to be susceptible to methicillin in spite of their carriage of mecA gene. In comparison,mecA-carrying strains in 1992 were mostly of single type in terms of production of type 2 coagulase (26 out of 27;96%), and high-level methicillin resistance (MIC50>-512). Clonal expansion of the coagulase type-2 strain was implicated under selective pressure of antibiotic usage during the last decade. Staphylococcus aureus clinical strains isolated in 1982 and 1992 at Tokyo University Hospital were studied for their carriage of mecA gene, antibiotic susceptibility patterns, toxin production, coagulase isotypes, and ribotyping patterns. The mecA-carrying strains in 1982 were mostly producers of type-4 coagulase (21 out of 31;68%), but producers of other coagulase types (type-1,-2,-7) were also found. The degree of methicillin resistance varied but was moderate with these strains (MIC50=16; range, 0.5–512 μg/ml at 32°C with 2% NaCl), and some strains were even judged to be susceptible to methicillin in spite of their carriage of mecA gene. In comparison,mecA-carrying strains in 1992 were mostly of single type in terms of production of type 2 coagulase (26 out of 27;96%), and high-level methicillin resistance (MIC50>-512). Clonal expansion of the coagulase type-2 strain was implicated under selective pressure of antibiotic usage during the last decade.