An epidemiologic survey of methicillin-resistant Staphylococcus aureus by combined use of mec-HVR genotyping and toxin genotyping in a university hospital in Japan

Objective:To evaluate the usefulness of an assay using two polymerase chain reaction-based genotyping methods in the practical surveillance of methicillin-resistantStaphylococcus aureus(MRSA).Methods:Nosocomial infection and colonization were surveyed monthly in a university hospital in Japan for 20 months. Genotyping withmec-HVR is based on the size of themec-associated hypervariable region amplified by polymerase chain reaction. Toxin genotyping uses a multiplex polymerase chain reaction method to amplify eight staphylococcal toxin genes.Results:Eight hundred nine MRSA isolates were classified into 49 genotypes. We observed differing prevalences of genotypes for different hospital wards, and could rapidly demonstrate the similarity of genotype for outbreak isolates. The incidence of genotype D: SEC/TSST1 was significantly higher in isolates causing nosocomial infections (49.5%; 48 of 97) than in nasal isolates (31.4%; 54 of 172) (P= .004), suggesting that this genotype may represent the nosocomial strains.Conclusion:The combined use of these two genotyping methods resulted in improved discriminatory ability and should be further investigated.