Epidemiology of Methicillin-resistant Staphylococcus aureus Pneumonia in Community Hospitals

Sarah S. Lewis, MD, MPH; Vanessa J. Walker, DO; Mi Suk Lee, MD; Luke Chen, MBBS, MPH; Rebekah W. Moehring, MD, MPH; Christopher E. Cox, MD, MHA, MPH; Daniel J. Sexton, MD; Deverick J. Anderson, MD, MPH

Disclosures

Infect Control Hosp Epidemiol. 2014;35(12):1452-1457. 

In This Article

Abstract and Introduction

Abstract

Objective Describe the epidemiology of healthcare-related (ie, healthcare-associated and hospital-acquired) pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) among hospitalized patients in community hospitals.

Design Retrospective cohort study.

Setting Twenty-four community hospitals in the southeastern United States affiliated with the Duke Infection Control Outreach Network (median size, 211 beds; range, 103–658 beds).

Methods Adult patients with healthcare-related MRSA pneumonia admitted to study hospitals from January 1, 2008, to December 31, 2012, were identified using surveillance data. Seasonal and annual incidence rates (cases per 100,000 patient-days) were estimated using generalized estimating equation models. Characteristics of community-onset and hospital-onset cases were compared.

Results A total of 1,048 cases of healthcare-related pneumonia due to MRSA were observed during 5,863,941 patient-days. The annual incidence rate of healthcare-related MRSA pneumonia increased from 11.3 cases per 100,000 patient-days (95% confidence interval [CI], 6.8–18.7) in 2008 to 15.5 cases per 100,000 patient-days (95% CI, 8.4–28.5) in 2012 (P = .055). The incidence rate was highest in winter months and lowest in summer months (15.4 vs 11.1 cases per 100,000 patient-days; incidence rate ratio, 1.39 [95% CI, 1.06–1.82]; P = .016). A total of 814 cases (77.7%) were community-onset healthcare-associated pneumonia cases; only 49 cases (4.7%) were ventilator-associated cases. Of 811 patients whose disposition was known, 240 (29.6%) died during hospitalization or were discharged to hospice.

Conclusions From 2008 through 2012, the incidence of healthcare-related MRSA pneumonia among patients who were admitted to a large network of community hospitals increased, despite the decreasing incidence of invasive MRSA infections nationwide. Additional study is warranted to evaluate trends in this important and potentially modifiable public health problem.

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of pneumonia in healthcare-exposed patients, and it accounts for more than 20% of cases of hospital-acquired pneumonia (HAP) and healthcare-associated pneumonia (HCAP).[1–4] Invasive infections due to MRSA are associated with excess morbidity and mortality and high costs to the healthcare system.[5] For example, in one case series, approximately 1 in 3 patients with HCAP or HAP due to MRSA died within 30 days of their infection.[6]

The epidemiology of severe infections caused by MRSA has changed in the last 2 decades. Although the incidence of MRSA pneumonia and other invasive infections caused by MRSA increased in the 1990s and 2000s, due in part to the emergence of a more virulent community-acquired MRSA strain,[3,7] more recent data demonstrate that the incidence of serious infections due to MRSA has decreased since 2005 in numerous settings.[8–12] The reason for the recent downtrend is not fully understood but may relate to a multitude of factors, including increased awareness and efforts to reduce transmission of infections in healthcare settings.[12]

Most data on the epidemiology of pneumonia in healthcare-exposed patients are derived from tertiary care centers, academic hospitals, and major urban settings.[4,6,13] However, approximately half of US hospitalizations occur in nonteaching hospitals.[14] To our knowledge, no data have been published regarding the epidemiology of MRSA pneumonia in the community hospital setting. Thus, the objective of our study was to describe the epidemiology of MRSA pneumonia among healthcare-exposed patients admitted to community hospitals.

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