Genetic Determinants of Methicillin Resistance and Virulence among Staphylococcus aureus Isolates Recovered from Clinical and Surveillance Cultures in a Brazilian Teaching Hospital

Abstract

Aims . To quantify the presence of SCC mec types and virulence genes among Staphylococcus aureus colonizing and infecting patients from a teaching hospital. Methods . We analyzed 225 and 84 S. aureus isolates recovered from surveillance and clinical cultures, respectively. Strains were studied for the presence and type of SCC mec , as well as for several virulence genes. Univariate and multivariable analysis were performed in order to identify predictors of invasiveness (defined as isolation from clinical cultures). Results . The presence of SCC mec types III (OR, 2.19, 95% CI, 1.08–4.45) and IV (OR, 5.28 95% CI, 1.35–20.63) and of genes coding for exfoliative toxin B ( etb , OR, 6.38, 95% CI, 1.48–27.46) and Panton-Valentine leukocidin ( pvl , OR, 2.38, 95% CI, 1.16–4.86) was independently associated with invasiveness. Conclusions . SCC mec types III and IV and virulence genes are associated with greater invasiveness of S. aureus . Patients colonized with methicillin-resistant S. aureus , as well as with strains harboring etb or pvl , may be prone to develop invasive disease. Infection-preventing strategies should be more intensively applied to this group.