Epidemiology of Community-Onset Staphylococcus aureus Bacteremia.

James Yarovoy,Heather Young,Bryan Knepper,Andrew Monte

doi:10.5811/westjem.2019.2.41939

Abstract

IntroductionStaphylococcus aureus bacteremia (SAB) is the second-most common cause of community-onset (CO) bacteremia. The incidence of methicillin-resistant S. aureus (MRSA) has recently decreased across much of the United States, and we seek to describe risk factors for CO-MRSA bacteremia, which will aid emergency providers in their choice of empiric antibiotics.MethodsThis is a retrospective cohort study of all patients with SAB at a 500-bed safety net hospital. The proportion of S. aureus isolates that were MRSA ranged from 32–35% during the study period. Variables of interest included age, comorbid medical conditions, microbiology results, antibiotic administration, duration of bacteremia, duration of hospital admission, suspected source of SAB, and Elixhauser comorbidity score. The primary outcome was to determine risk factors for CO-MRSA bacteremia as compared to methicillin-susceptible S. aureus (MSSA) bacteremia in patients admitted to the hospital through the emergency department.ResultsWe identified 135 consecutive patients with CO-SAB. In comparison to those with MSSA bacteremia, patients with MRSA bacteremia were younger (odds ratio [OR] 0.5, 95% confidence interval [CI], 0.4–0.7) with higher Elixhauser comorbidity scores (OR 1.4, 95% CI, 1.1–1.7). Additionally, these patients were more likely to have a history of MRSA infection or colonization (OR 8.9, 95% CI, 2.7–29.7) and intravenous drug use (OR 2.4, 95% CI, 1.0–5.7).ConclusionSAB continues to be prevalent in our urban community with CO-MRSA accounting for almost one-third of SAB cases. Previous MRSA colonization was the strongest risk factor for current MRSA infection in this cohort of patients with CO-SAB.

Highlights

Staphylococcus aureus bacteremia (SAB) is the second-most common cause of community-onset (CO) bacteremia
The primary outcome was to determine risk factors for CO-methicillin-resistant S. aureus (MRSA) bacteremia as compared to methicillin-susceptible S. aureus (MSSA) bacteremia in patients admitted to the hospital through the emergency department
SAB continues to be prevalent in our urban community with CO-MRSA accounting for almost one-third of SAB cases

Summary

Introduction

Staphylococcus aureus bacteremia (SAB) is the second-most common cause of community-onset (CO) bacteremia. Staphylococcus aureus bacteremia (SAB) is the secondmost common cause of community-onset (CO) bacteremia, affecting 15-40 per 100,000 population per year.[1,2] It is associated with a 20% mortality rate[3,4] with higher mortality linked to the presence of methicillin resistance, comorbid conditions, intensive care unit admission, and prior exposure to antibiotics.[5] Three-quarters of SAB are CO bacteremia, with the majority being secondary to skin and soft tissue infections. MRSA was identified as a healthcare-associated pathogen.[7] In the late 1980s, community-onset MRSA, primarily the USA300 strain, was first identified. It spread throughout healthy community members including children, athletes, military personnel, and inmates in the 1990s.8,9. It spread throughout healthy community members including children, athletes, military personnel, and inmates in the 1990s.8,9 By the mid-

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