Clinical features of bloodstream infections caused by the two dominant clones of endemic methicillin-resistant Staphylococcus aureus

Abstract

Background We evaluated the molecular epidemiology of methicillin-resistant S. aureus (MRSA) bloodstream infections (BSIs) through an in-depth analysis of BSIs caused by the two dominant clones circulating in New York City at a large urban tertiary- and quaternary-care teaching hospital. Methods Comprehensive clinical data extraction from the electronic health records of 227 hospitalized patients ≥18 years old with MRSA bacteremia between August 2014 through April 2017 was collected. The descriptive epidemiology and mortality associated with the two dominant clonal complexes (CCs) was compared using logistic regression. Results Analysis revealed that 91% of all single-patient MRSA BSIs were due to two equally represented genotypes, the CC5 (N=117) and the CC8 (N=110). The CC8 caused disease more frequently in younger age groups (60 ± 17 vs 70 ± 17 years old; p<0.001) and in non-White race (OR=3.21 95% CI [1.42-7.22]; p=0.005). The CC8 caused BSI more frequently in the setting of peripheral intravenous catheters infections (OR=6.46; 95% CI [1.68-24.87]; p=0.007). MRSA BSIs were associated with 90-day mortality of 27%. Conclusions The clinical features distinguishing the two dominant MRSA clones continue to converge. The association of CC8 with peripheral intravenous catheters infections underscores the importance of classical community clones causing hospital-onset infections. Ongoing monitoring and analysis of the dynamic epidemiology of this endemic pathogen is crucial to inform management to prevent invasive disease.