[Staphylococcal cassette chromosome mec types and antimicrobial susceptibilities of methicillin-resistant Staphylococcus aureus isolated from our hospital].

Abstract

Reports of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have recently increased in Japan. To determine the status of MRSA infections in our hospital, we investigated their Staphylococcal cassette chromosome mec (SCCmec) types and prevalence of Panton-Valentine leukocidin (PVL). In addition, we investigated the relation between their SCCmec and antimicrobial susceptibility. The 191 strains were isolated from January to July in 2011 and were classified as SCCmec type I (2, 1.0％), type II (136, 71.2％), type IV (36, 18.8％), type V (4, 2.1％) and type VIII (2, 1.0％). Eleven isolates (5.8％) were designated as nontypable. No isolates were PVL-positive in this study. The SCCmec type IV strains were more susceptible to imipenem (MIC90, 0.25 μg/ml) than SCCmec type II strains (MIC90, >16 μg/ml). This difference was also observed between SCCmec type IV and SCCmec type II in susceptibility levels to clarithromycin, clindamycin, minocycline, and levofloxacin, but not to gentamicin. In particular, SCCmec type IV strains were susceptible to imipenem and minocycline. The result indicates these susceptibility is useful to discriminate CA-MRSA from Hospital-associated MRSA (HA-MRSA).