Population-based Evaluation of Patients with Methicillin-resistant Staphylococcus aureus (MRSA) Infection in Relation to Animal Feeding Operations in Pennsylvania

November 30, 2011 — 

New MRSA strains and epidemiologic patterns of infection have emerged in the past decade, with community-associated patterns now dominant. In Europe, these new community strains have been linked to animal feeding operations (AFOs), raising concerns about the widespread use of non-therapeutic antibiotics in animal feeds. No prior population-based studies have evaluated the risk of MRSA infection in relation to AFOs in the U.S. Methods We used Geisinger Clinic electronic health record data from 2001 to February 2010 on all primary care patients (n = 440,000). Three groups of patients were identified using specific ICD-9 codes: Community-onset MRSA (CO-MRSA) without risk factors (i.e., infection diagnosed as an outpatient, no antibiotics or hospitalizations in the prior year, no household contacts, no history of MRSA colonization); Hospital-onset MRSA (HO-MRSA) with risk factors (i.e., diagnosed in the hospital with at least one MRSA risk factor); and Skin infection (e.g., cellulitis, carbuncle, skin abscess) without MRSA infection or colonization history and without MRSA risk factors. MRSA cases were frequency-matched to controls with no history of MRSA or risk factors. Information on concentrated animal feeding operations (CAFOs) were obtained from the Pennsylvania Department of Environmental Protection, and included data on animal species (e.g., swine, dairy cattle, chickens), counts, animal equivalent units (AEUs), farm acreage, and manure generated, exported, and stored. Measures of density (e.g., AEUs per sq. mi. in township) and accessibility (e.g., distance from residence to nearest CAFO, gravity models) were derived and used in logistic regression models comparing the four groups. Results A total of 1926 MRSA cases were identified from 2003 to 2010. Of these, 1058 (55%) were identified in outpatient records, 530 (28%) from inpatient records, and 290 (15%) from medication orders. Inpatient cases increased from 2 in 2003 to 88 in 2005, remained at the same frequency through 2008, and then increased to 116 in 2009. In contrast, outpatient cases increased steadily from 4 in 2003 to a peak of 325 in 2008. Conclusions The data clearly show a steady increase in the incidence of CO-MRSA in this region. Relations with AFOs will be presented and discussed.

Schwartz B, Pollak J, Mercer D, Dewalle J, Stewart W, PS2-36: Population-based Evaluation of Patients with Methicillin-resistant Staphylococcus aureus (MRSA) Infection in Relation to Animal Feeding Operations in Pennsylvania, Clin Med Res. 2011 Nov;9(3-4):166.