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Advance Publication

Environ Health Perspect; DOI:10.1289/ehp.1307370

High-Density Livestock Production and Molecularly Characterized MRSA Infections in Pennsylvania

Joan A. Casey,1,2 Bo Shopsin,3 Sara E. Cosgrove,4 Keeve E. Nachman,1,2 Frank C. Curriero,1,5 Hannah R. Rose,3 and Brian S. Schwartz1,6,7 
Author Affiliations close
1Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA; 2Center for a Livable Future, Johns Hopkins University, Baltimore, Maryland, USA; 3 Department of Medicine, New York University School of Medicine, New York, New York, USA; 4Division of Infectious Disease, Johns Hopkins School of Medicine, Baltimore, Maryland, USA; 5Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA; 6Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA; 7Center for Health Research, Geisinger Health System, Danville, Pennsylvania, USA
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This EHP Advance Publication article has been peer-reviewed, revised, and accepted for publication. EHP Advance Publication articles are completely citable using the DOI number assigned to the article. This document will be replaced with the copyedited and formatted version as soon as it is available. Through the DOI number used in the citation, you will be able to access this document at each stage of the publication process.

Citation: Casey JA, Shopsin B, Cosgrove SE, Nachman KE, Curriero FC, Rose HR, Schwartz BS. High-Density Livestock Production and Molecularly Characterized MRSA Infections in Pennsylvania. Environ Health Perspect;

Received: 15 July 2013
Accepted: 6 February 2014
Advance Publication: 7 February 2014

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Background: European studies suggest that living near high-density livestock production increases the risk of sequence type ST398 methicillin-resistant Staphylococcus aureus (MRSA) colonization. To our knowledge, no studies have evaluated associations between livestock production and human infection by other strain types.

Objectives: We evaluated associations between MRSA molecular subgroups and high-density livestock production.

Methods: We conducted a yearlong 2012 prospective study on a stratified random sample of patients with culture-confirmed MRSA infection; we oversampled patients from the Geisinger Health System with exposure to high-density livestock production in Pennsylvania. Isolates were characterized using S. aureus protein A (spa) typing and detection of Panton-Valentine leukocidin and scn genes. Patients with one of two specific MRSA strains were compared to patients with all other strains of MRSA isolates using logistic regression that accounted for the sampling design, for two different exposure models: one based on the location of the animals (livestock model) and the other on crop field application of manure (crop field model).

Results: Of 196 MRSA isolates, we identified 30 spa types, 47 PVL-negative and 15 scn-negative isolates, and no ST398 MRSA. Compared with quartiles 1-3 combined, the highest quartiles of swine livestock and dairy/veal crop field exposures were positively associated with community-onset-PVL-negative MRSA (CO-PVL-negative MRSA versus all other MRSA), with adjusted odds ratios of 4.24 (95% CI: 1.60, 11.25) and 4.88 (95% CI: 1.40, 17.00), respectively. The association with CO-PVL-negative MRSA infection increased across quartiles of dairy/veal livestock exposure (trend p = 0.05).

Conclusions: The findings suggest that other MRSA strains, beyond ST398, may be involved in livestock-associated MRSA infection in the U.S.

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