Genotyping of skin and soft tissue infection (SSTI)-associated methicillin-resistant Staphylococcus aureus (MRSA) strains among outpatients in a teaching hospital in Japan: application of a phage-open reading frame typing (POT) kit

Abstract We aimed to elucidate the current epidemiological features of outpatient skin and soft tissue infection (SSTI)-associated methicillin-resistant Staphylococcus aureus (MRSA) in Japan. Altogether, we evaluated the performance of a phage-open reading frame typing (POT) kit for genotyping these MRSA strains. We collected 57 MRSA strains from all outpatients with SSTIs attending a teaching hospital in Japan. Drug susceptibility measurement and genotyping including SCC mec typing, spa typing, multilocus sequence typing, pulsed-field gel electrophoresis, and commercial POT-kit were performed. The majority of strains (39 strains, 68 %) had the SCC mec -II element. Seventeen strains (30 %) with SCC mec -IV accounted for the second largest population. Strains with SCC mec -IV and SCC mec -V appeared multiclonal, and a predominance of Panton–Valentine leukocidin (PVL) gene-negative CC8/ spa -CC008 strains, as well as the first isolate of an ST93 strain in Japan, was observed among them. Only one USA300 strain was identified. Strains with SCC mec -IV and SCC mec -V were significantly susceptible to antimicrobials. The PVL gene was found in 5 SCC mec -IV strains and 1 SCC mec -V strain. The POT-kit successfully predicted the SCC mec type in 54 strains (95 %), and typing by POT1 scores was highly concordant with SCC mec typing and spa typing. Moreover, three PVL-positive strains fell into a particular POT type (POT scores, 106–77–113). Simpson’s index of the POT-kit was 0.977. In conclusion, the present study clarified the multiclonal nature of outpatient SSTI-associated MRSA in a teaching hospital in Japan. These data also underscore the utility of the POT-kit for non-outbreak surveillance through its simple platform consisting of two multiplex PCRs without sequencing.