Epidemiology and Outcome of Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus (MRSA) in Canadian Hospitals

Manal Tadros,Ethan Rubinstein,Harris Iacovides,Shariq Haider,Victoria Williams,Kathryn N Suh,Stephanie Smith,Jeff Powis,Michael John,Brenda L Coleman,Andrew E Simor,Christine Watt,Christine Lee,Nancy Laffin,Kevin Katz,Shelly Mcneil,Lynn Johnston,Allison Mcgeer ,Grahame S Taylor

doi:10.1371/journal.pone.0075171

Abstract

BackgroundMRSA remains a leading cause of hospital-acquired (HAP) and healthcare-associated pneumonia (HCAP). We describe the epidemiology and outcome of MRSA pneumonia in Canadian hospitals, and identify factors contributing to mortality.MethodsProspective surveillance for MRSA pneumonia in adults was done for one year (2011) in 11 Canadian hospitals. Standard criteria for MRSA HAP, HCAP, ventilator-associated pneumonia (VAP), and community-acquired pneumonia (CAP) were used to identify cases. MRSA isolates underwent antimicrobial susceptibility testing, and were characterized by pulsed-field gel electrophoresis (PFGE) and Panton-Valentine leukocidin (PVL) gene detection. The primary outcome was all-cause mortality at 30 days. A multivariable analysis was done to examine the association between various host and microbial factors and mortality.ResultsA total of 161 patients with MRSA pneumonia were identified: 90 (56%) with HAP, 26 (16%) HCAP, and 45 (28%) CAP; 23 (14%) patients had VAP. The mean (± SD) incidence of MRSA HAP was 0.32 (± 0.26) per 10,000 patient-days, and of MRSA VAP was 0.30 (± 0.5) per 1,000 ventilator-days. The 30-day all-cause mortality was 28.0%. In multivariable analysis, variables associated with mortality were the presence of multiorgan failure (OR 8.1; 95% CI 2.5-26.0), and infection with an isolate with reduced susceptibility to vancomycin (OR 2.5, 95% CI 1.0-6.3).ConclusionsMRSA pneumonia is associated with significant mortality. Severity of disease at presentation, and infection caused by an isolate with elevated MIC to vancomcyin are associated with increased mortality. Additional studies are required to better understand the impact of host and microbial variables on outcome.

Highlights

Methicillin-resistant Staphylococcus aureus (MRSA) is among the most frequently identified pathogens causing healthcare-associated pneumonia (HCAP), hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP) worldwide [1,2]
The objectives of this study were to describe the epidemiology and outcomes associated with MRSA pneumonia in adults in Canadian hospitals, and to identify host and microbial variables associated with mortality
Variables considered in the model were selected a priori based on previously published data [9,13,25], and included age, presence of underlying comorbidities, pneumonia acquisition (CAP or HCAP/HAP), presence of MRSA bacteremia or multiorgan failure, use of appropriate empiric antimicrobial therapy, infecting strain of MRSA with the Panton-Valentine leukocidin (PVL) gene, or with reduced susceptibility to vancomcyin

Summary

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is among the most frequently identified pathogens causing healthcare-associated pneumonia (HCAP), hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP) worldwide [1,2]. It appears to be a relatively uncommon cause of community-acquired pneumonia (CAP). The epidemiology of MRSA pneumonia is not well understood, and in particular, the relative importance of host and microbial factors in affecting its outcome is uncertain. Host factors such as underlying comorbidities or measures of severity of illness have been associated with poor outcome [9,10]. We describe the epidemiology and outcome of MRSA pneumonia in Canadian hospitals, and identify factors contributing to mortality

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