Staphylococcus aureus Nasal Carriage among Beefpacking Workers in a Midwestern United States Slaughterhouse.

Jessica H Leibler,Lance B Price,Jeanne A Jordan,Kirsten Brownstein,Melissa J Perry,Lina Lander,Karsten Becker

doi:10.1371/journal.pone.0148789

Abstract

Occupational contact with livestock is an established risk factor for exposure to livestock-associated methicillin-resistant Staphylococcus aureus (MRSA), particularly among industrial swine workers. While S. aureus is known to infect cattle, livestock-associated S. aureus carriage among workers in the beef production chain has received limited attention. Beefpacking workers, who slaughter, butcher and process cattle, have intensified exposure to potentially infectious animal materials and may be at risk of livestock-associated S. aureus exposure. We conducted a cross-sectional study of beefpacking workers (n = 137) at an industrial slaughterhouse in the Midwestern United States to evaluate prevalence and characteristics of S. aureus nasal colonization, specifically the absence of the scn gene to identify putative association with livestock, antibiotic susceptibility, presence of Panton-Valentin leukocidin (PVL) genes lukS-PV and lukF-PV, and spa type. Overall prevalence of S. aureus nasal carriage was 27.0%. No workers carried livestock-associated MRSA. Methicillin-sensitive S. aureus isolates (MSSA) recovered from five workers (3.6%) lacked the scn gene and were considered putative livestock-associated S. aureus (pLA-SA). Among pLA-SA isolates, spa types t338, t748, t1476 and t2379 were identified. To our knowledge, these spa types have not previously been identified as associated with livestock. Prevalence of human-adapted MRSA carriage in workers was 3.6%. MRSA isolates were identified as spa types t002, t008 and t024, and four of five MRSA isolates were PVL-positive. To date, this is the first study to indicate that industrial beefpacking workers in the United States may be exposed to livestock-associated S. aureus, notably MSSA, and to spa types not previously identified in livestock and livestock workers. Occupational exposure to livestock-associated S. aureus in the beef production chain requires further epidemiologic investigation.

Highlights

Staphylococcus aureus is known to colonize many livestock species, including swine, poultry, sheep and cattle [1,2,3]
While much of the research on LA-methicillin-resistant S. aureus (MRSA) focuses on nasal carriage among swine workers, less is known about S. aureus colonization among workers in the beef production chain
Five workers in our study (3.6%) were nasal carriers Methicillin-sensitive S. aureus isolates (MSSA) with putative association with livestock. These putative livestock-associated S. aureus (pLA-SA) isolates represented distinct spa types (t338, t748, t1476, t2379) that are associated with strains not previously identified in livestock, to our knowledge

Summary

Introduction

Staphylococcus aureus is known to colonize many livestock species, including swine, poultry, sheep and cattle [1,2,3]. While much of the research on LA-MRSA focuses on nasal carriage among swine workers, less is known about S. aureus colonization among workers in the beef production chain. MRSA carriage has been documented in beef cattle, veal calves, and dairy cattle, and MRSA isolates have been recovered in bulk milk and consumer beef products [12,17,18,19,20,21,22]. Four studies in the Netherlands identified prevalence of MRSA nasal carriage ranging from 3.9% to 24.8% among beef cattle in that country, with elevated prevalence noted among veal calves compared to beef and dairy cattle [21,23,24,25]. In studies of S. aureus carriage among beef cattle, the majority of isolates have been identified as ST398, mostly spa types t011 and t034, spa types not associated with ST398 have been recovered from beef and carcasses, including t1430 and t008 [26]

Methods

Results

Conclusion