[Impact of methicillin resistance on mortality and surveillance of vancomycin susceptibility in bacteremias caused by Staphylococcus aureus].

Staphylococcus aureus is a major nosocomial pathogen that causes severe morbidity and mortality in many hospitals worldwide. Besides, the incidence of S. aureus bacteremia has significantly increased over the past decades. The aims of this study were to detect the risk factors for methicillin resistance and mortality and to evaluate vancomycin susceptibility in methicillin-resistant isolates. Thus, 39 S. aureus isolates from blood cultures of hospitalized patients with bacteremia were studied in Nueva Clínica Chacabuco Tandil, Buenos Aires, Argentina during 01/2006-12/2008. The overall mortality was 51.3%, which was significantly associated with methicillin resistance (OR: 4.20, IC95%: 1.08-16.32, p: 0.05), even though it was not an independent mortality predictor as it was the mechanical ventilation (OR: 15.99, IC95%: 3.24 - 78.86). Previous surgery (OR: 17.23, IC95%: 1.80-164.60) and hospitalization in intensive care units (OR: 21.12, IC95%: 2.33-191.30) were independent predictors of meticillin-resistance. No isolates were found with reduced vancomycin susceptibility. All the studied isolates were in vitro susceptible to vancomycin with a MIC50 and MIC90 of 0.5 μg/ml.