Coexistence of virulence genes in methicillin-resistant Staphylococcus aureus clinical isolates

The pathogenic versatility of Staphylococcus aureus is attributed to various virulence genes, including enterotoxins and hemolysins. Here, the virulence genes in 177 nosocomial MRSA strains in Porto Alegre, Brazil were detected by PCR. The overall prevalence rates were as follows: sea, 4.5%; pvl, 18.6%; tst, 27.7%; hla, 87.6%; and hld, 90.4%. No strain contained all tested genes. However, there was frequent coexistence of tst with pvl and hla with hld (40.7% and 26.6%, respectively). Horizontal transfer of virulence genes is very common in S. aureus, as suggested by the frequent coexistence of several virulence genes.