Thirty-day mortality in UK patients with community-onset and hospital-acquired meticillin-susceptible Staphylococcus aureus bacteraemia

Abstract

Background: The difference in mortality between patients with community-onset and hospital-acquired Staphylococcus aureus infections has rarely been described and where it has, results have been conflicting.

Aim: To determine 30-day mortality in consecutive patients with meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia and the association between community-onset infection and outcome.

Methods: From August 2007 to July 2011, demographic, clinical and microbiological data were prospectively collected on patients with MSSA bacteraemia. Patients were followed until death, hospital discharge or recovery from infection. Multivariate logistic regression was used to determine the association between community-onset infection and 30-day mortality.

Findings: A total of 403 bacteraemic episodes occurred in 392 patients. Overall, there were 44 deaths (11.2%; 95% confidence interval: 7.9-14.0%) at 7 days and 101 deaths (25.8%; 21.5-30.4%) at 30 days. The difference in 30-day mortality between patients with community-onset and hospital-acquired infection was 71/256 (27.7%) versus 31/147 21.1%). Community-onset infection more frequently caused infective endocarditis (13/14, 92.9%), vertebral osteomyelitis (12/13, 92.3%) and skin and soft tissue infection (61/71, 85.9%) whereas intravascular catheter-associated infections were predominantly hospital-acquired (60/82, 73.2%). Age, Pitt score, Charlson comorbidity index (CCI), specific sites of infection (skin and soft tissue, lower respiratory tract and peripheral joints) and delay in appropriate treatment were strongly associated with 30-day mortality. In multivariate analysis, after adjustment for age, CCI and delay in appropriate treatment, community-onset infection was strongly associated with 30-day mortality (odds ratio: 1.59; 95% confidence interval: 0.91-2.80).

Conclusions: Compared with hospital-acquired MSSA bacteraemic infection, community-onset infection was associated with worse 30-day outcomes. Hospital-acquired MSSA bacteraemic infections were rarely metastatic, frequently associated with medical devices and patients had better outcomes.