Clinical characteristics of bloodstream infections associated with endemic Methicillin-resistant Staphylococcus aureus clones

Background: Methicillin-resistant Staphylococcus aureus (MRSA) causes life-threatening infections in both community and hospital settings and is a leading cause of healthcare-associated infections (HAIs). We sought to describe the molecular epidemiological landscape of patients with MRSA bloodstream infections (BSIs) at an urban medical center by evaluating the clinical characteristics associated with infection with the major endemic clones.Methods: Extensive clinical data extraction from the electronic health records of 225 patients (August 2014 to April 2017) with MRSA bacteremia was collected. The descriptive epidemiology and mortality associated with the two dominant clonal complexes (CCs) was compared by univariate and multivariate analyses of clinical features as well as stratified analysis by HAI definitions.Results: Analysis of first positive, single-patient MRSA isolates revealed that 91% of the MRSA BSIs were one of two genotypes, CC5 (N=116) or CC8 (N=109). The MRSA BSIs were associated with high all-cause in-hospital (23%) and overall (39%) mortality. Aside from the association between age and CC5, few of the other 45 variables reached statistical significance. One notable exception was peripheral intravenous catheters as infection source, which was associated with the CC8 clone (OR=6.27 95% CI [1.72-22.90]). Conclusions: The descriptive epidemiology of MRSA BSIs in a quaternary urban facility revealed few clinical features distinguish BSIs with the major MRSA clones. The CC8 was associated with infection with peripheral intravenous catheters, suggesting skin colonization from the community presenting as a hospital-onset infection. Ongoing monitoring and analysis of the dynamic epidemiology of this endemic pathogen is crucial to inform management and forestall disease.