Increased mortality among elderly patients with meticillin-resistant Staphylococcus aureus bacteraemia

Abstract

Despite the high prevalence of meticillin-resistant Staphylococcus aureus (MRSA) infections among the elderly, outcomes of nosocomial MRSA bloodstream infections (BSI) for this patient population have not been fully examined. We performed a case-control study to compare outcomes of hospital-acquired MRSA BSI among patients >/=65 years of age (cases) with those younger than 65 years of age (controls). In a 430-bed tertiary-care teaching hospital, 100 hospitalized patients >/=18 years of age with S. aureus BSI were included in the study. Measurements obtained were: comorbidities, severity of illness at presentation, antibiotic therapy, haematogenous complications and mortality. Overall mortality was significantly higher among cases than controls [36% vs 12%; odds ratio (OR) 4.1, 95% confidence interval (CI) 1.4-14, P<0.01]. A pulmonary source was identified more frequently among elderly patients compared with younger controls (34% vs 16%; OR 2.7, 95%CI 1.1-8.1, P=0.04). On logistic regression, the following variables were independently associated with MRSA BSI among elderly patients: admission to a medical ward (OR 3.1, 95%CI 1.3-7.6, P=0.02), non-central-venous-catheter-related BSI (OR 3, 95%CI 1.2-7.6, P=0.02) and death (OR 3.7, 95%CI 1.3-11, P=0.02). Among patients who received vancomycin, more cases were treated with a reduced dose of vancomycin due to renal insufficiency compared with controls (64% vs 31%; OR 4, 95%CI 2-9, P=0.01). These data suggest that MRSA BSI is associated with significant mortality among the elderly population. Preventing MRSA acquisition among this patient population is of paramount importance.