title: Air exposure as a possible route for ESBL in pig farmers.
abstract: Livestock can carry extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, with blaCTX-M-1being most prevalent. ESBL carriage in farmers is associated with ESBL carriage in animals, with direct animal-human contact considered as the dominant route of transmission. However, inhalation of stable air might represent another route of transmission. We, therefore, quantified presence of blaCTX-Mgroup 1 genes (CTX-M-gr1) in dust and the association with CTX-M-gr1 carriage in pig farmers, family members and employees. We included 131 people living and/or working on 32 conventional Dutch pig production farms (farmers, family members and employees) during two sampling moments over a 12-month interval. Human stool samples, rectal swabs from 60 pigs per farm, and 2-5 dust samples collected using an electrostatic dust collector (EDC) (as a proxy for presence of viable CTX-M-gr1 carrying bacteria in air) were obtained per farm. Presence of ESBL-producing Escherichia Coli (E. coli) in stool samples and rectal swabs was determined by selective plating and CTX-M-gr1 was identified by PCR. Dust samples were analyzed directly by PCR for presence of CTX-M-gr1. Questionnaires were used to collect information on nature, intensity and duration of animal contact. Overall human prevalence of CTX-M-gr1 carriage was 3.6%. CTX-M-gr1 was detected in dust on 26% of the farms and in pigs on 35% of the farms, on at least one sampling moment. Human CTX-M-gr1 carriage and presence of CTX-M-gr1 in dust were associated univariately (OR=12.4, 95% CI=2.7-57.1). In multivariate analysis human CTX-M-gr1 carriage was associated with the number of working hours per week (OR=1.03, 95% CI=1.00-1.06), presence of CTX-M-gr1 carrying pigs on the farm (OR=7.4, 95% CI=1.1-49.7) and presence of CTX-M-gr1 in dust (OR=3.5, 95% CI=0.6-20.9). These results leave open the possibility of airborne CTX-M-gr1 transmission from animals to humans next to direct contact.
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands. Electronic address: w.dohmen@uu.nl.
authors.forename: Wietske
authors.initials: W
authors.lastname: Dohmen
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Heike
authors.initials: H
authors.lastname: Schmitt
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marc
authors.initials: M
authors.lastname: Bonten
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Dick
authors.initials: D
authors.lastname: Heederik
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000032:analysis*; D000818:Animals; D004269:DNA, Bacterial / Q000032:analysis; D004391:Dust / Q000032:analysis*; D004784:Environmental Monitoring; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000032:analysis*; D000067565:Farmers; D005243:Feces / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D016273:Occupational Exposure / Q000032:analysis*; D013552:Swine; D055815:Young Adult; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D004269:DNA, Bacterial; D004391:Dust; D029968:Escherichia coli Proteins; D001618:beta-Lactamases; C000602253:beta-lactamase CTX-M, E coli
keywords: Airborne transmission; Antimicrobial resistance; Extended-spectrum beta-lactamase; Pig farmers; Zoonosis