Oxacillin Resistance of Staphylococcus aureus Isolated from the University Hospital of Botucatu Medical School in Brazil

Background: Oxacillin is the main drug used for the treatment of Staphylococcus aureus infections. However, resistance of S. aureus to oxacillin has become a major problem over recent decades. The aim of this study was to determine oxacillin resistance in S. aureus isolates obtained from the University Hospital of the Botucatu Medical School, Universidade Estadual Paulista, Brazil. Materials and Methods: A total of 102 isolates collected between 2002 and 2006 were analyzed by detection of the mecA gene, cefoxitin and oxacillin disk diffusion methods, screening test on Mueller-Hinton agar and E-test. Results: Forty-six (45.1%) isolates were mecA positive. The oxacillin disk diffusion method showed 86.9% sensitivity and 91.1% specificity. The screening method and cefoxitin disk diffusion presented a similar sensitivity (91.3%) and the same specificity. The E-test showed 97.8% sensitivity and the same specificity as observed for the other methods. Conclusions: The E-test yielded the best results compared to the other methods.