Distribution of Virulence Genes in spa Types of Methicillin-resistant Staphylococcus aureus Isolated from Patients in Intensive Care Units

BACKGROUND: Various virulence factors and superantigens are encoded by mobile genetic elements. The relationship between clonal background and virulence factors differs in different geographic regions. We compared the distribution and relationship of spa types and virulence genes among methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from a tertiary hospital in 2000-01 and 2007-08. METHODS: In 2000-01 and 2007-08, 94 MRSA strains were collected from 3 intensive care units at a Korean tertiary hospital. We performed spa typing and multiplex PCR for 19 superantigen genes. RESULTS: Relatively frequent spa types were t037 (40.5%), t002, t601, and t2138 in 2000-01, and t2460 (43.9%), t002, t037, t601, t324, and t2139 in 2007-08. We identified 4 novel spa types, 2 of which were designated as t5076 and t5079. Superantigen profiles were closely linked to spa types. For example, sea, sek, and seq superantigen genes were mainly detected in t037 strains. CONCLUSIONS: Major spa types differed depending on study periods, and the distribution of superantigen genes correlated with spa type.