Airborne Multidrug-Resistant Bacteria Isolated from a Concentrated Swine Feeding Operation Amy Chapin, Ana Rule, Kristen Gibson, Timothy Buckley, and Kellogg Schwab Johns Hopkins Bloomberg School of Public Health, Department of Environmental Health Sciences, Baltimore, Maryland, USA Abstract The use of nontherapeutic levels of antibiotics in swine production can select for antibiotic resistance in commensal and pathogenic bacteria in swine. As a result, retail pork products, as well as surface and groundwaters contaminated with swine waste, have been shown to be sources of human exposure to antibiotic-resistant bacteria. However, it is unclear whether the air within swine operations also serves as a source of exposure to antibiotic-resistant bacterial pathogens. To investigate this issue, we sampled the air within a concentrated swine feeding operation with an all-glass impinger. Samples were analyzed using a method for the isolation of Enterococcus. A total of 137 presumptive Enterococcus isolates were identified to species level using standard biochemical tests and analyzed for resistance to erythromycin, clindamycin, virginiamycin, tetracycline, and vancomycin using the agar dilution method. Thirty-four percent of the isolates were confirmed as Enterococcus, 32% were identified as coagulase-negative staphylococci, and 33% were identified as viridans group streptococci. Regardless of bacterial species, 98% of the isolates expressed high-level resistance to at least two antibiotics commonly used in swine production. None of the isolates were resistant to vancomycin, an antibiotic that has never been approved for use in livestock in the United States. In conclusion, high-level multidrug-resistant Enterococcus, coagulase-negative staphylococci, and viridans group streptococci were detected in the air of a concentrated swine feeding operation. These findings suggest that the inhalation of air from these facilities may serve as an exposure pathway for the transfer of multidrug-resistant bacterial pathogens from swine to humans. Key words: air sampling, airborne bacteria, antibiotic resistance, CAFO, concentrated swine feeding operation, multidrug-resistant bacteria. Environ Health Perspect 113:137-142 (2005) . doi:10.1289/ehp.7473 available via http://dx.doi.org/ [Online 22 November 2004] Address correspondence to K. Schwab, Johns Hopkins Bloomberg School of Public Health, Department of Environmental Health Sciences, 615 N. Wolfe St., Room E6620, Baltimore, MD 21205-2103 USA. Telephone: (410) 614-5753. Fax: (410) 955-9334. E-mail: kschwab@jhsph.edu We thank the swine grower for providing access to the swine operation. We also thank K. Carroll and D. Flayhart for speciating the bacterial isolates and reviewing the manuscript ; W. Merz for reviewing the manuscript ; and E. Silbergeld for reviewing the manuscript and providing many helpful insights. This research was supported by the Center for a Livable Future at the Johns Hopkins Bloomberg School of Public Health and the National Institute for Occupational Safety and Health, Education Research Center, Pilot Project Research Training Award (T42/CCT31049-09) . A.C. is a Howard Hughes Medical Institute Predoctoral Fellow. The authors declare they have no competing financial interests. Received 2 August 2004 ; accepted 22 November 2004. The full version of this article is available for free in HTML or PDF formats. |