Reduced Mortality of Staphylococcus aureus Bacteremia in a Retrospective Cohort Study of 2139 Patients: 2007–2015

Abstract

Abstract Background Understanding the changing epidemiology of Staphylococcus aureus bacteremia, as well as the variables associated with poor outcomes, can yield insight into potential interventions. Methods This study was a retrospective, observational cohort study of adult patients at an academic medical center in New York City who had S. aureus bloodstream infections between 1 January 2007 and 31 December 2015. Participants were divided into 3 periods: group 1 (2007–2009), group 2 (2010–2012), and group 3 (2013–2015) for trend analysis. All clinical strains were genotyped (spa.). The main outcome was 30-day all-cause mortality. Results There were 1264 episodes of methicillin-susceptible S. aureus (MSSA) and 875 episodes of methicillin-resistant S. aureus (MRSA) bacteremia, with a rising proportion due to MSSA (55% group 1; 59% group 2; 63% group 3; P = .03.) There were no significant changes in average age, gender, Charlson score, and distribution of strain genotypes. Mortality in MRSA infection was unchanged (25% group 1; 25% group 2; 26% group 3), while mortality in MSSA infection significantly declined (18% group 1; 18% group 2; 13% group 3). The average time to antistaphylococcal therapy (AST) in MSSA infection declined during the study (3.7 days group 1; 3.5 group 2; 2.2 group 3). In multivariate analysis, AST within 7 days of initial positive MSSA culture was associated with survival. Conclusions Mortality in MSSA bloodstream infection is declining, associated with a decrease in time to targeted therapy. These results emphasize the potential for rapid diagnostics and early optimization of treatment to impact outcomes in MSSA bacteremia.