A comparative study of patients with methicillin susceptible versus methicillin resistant Staphylococcus aureus bacteremia: epidemiology and prognostic factors

The influence of methicillin resistance in Staphylococcus aureus bacteremia (SAB) continues to be controversial. The aim of this study was to evaluate risk factors and mortality predictors in patients with SAB and the influence of methicillin resistance in mortality (SAMSB vs SAMRB). Prospective study including 213 in-patients with SAB. Of 213 episodes of SAB, 131 (61.5%) were due to SAMS and 82 (38.5%) to SAMR. Risk factors associated with SAMRB were: nosocomial infection, presence of an ultimately or rapidly fatal underlying disease, diabetes mellitus, intravenous catheters, previous ICU hospitalization and therapy with broad-spectrum antibiotics. Severity and complications were more frequent in patients with SAMRB. Mortality was 42.6% in SAMRB cases vs 16% in SAMSB cases (p < 0.05). Multivariate analysis showed as independent predictors of mortality in patients with SAB: presence of an ultimately or rapidly fatal underlying disease, acute severity of illness at onset and inappropriate empirical therapy; methicillin resistance was not an independent predictor of mortality. Methicillin resistance was not an independent predictor of mortality in patients with SAB. Presence of a fatal underlying disease, acute severity of illness at onset and inappropriate therapy were the main prognosis factors in patients with SAB.