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CRE presence on US swine farm poses threat of foodborne transmission
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Researchers detected carbapenem-resistant Enterobacteriaceae among swine at a farrow-to-finish barn in the United States, according to a recently published study.
While CRE have been reported in livestock from Europe and Asia, this is the first instance in which they have been identified among US livestock, raising concerns about the possibility of foodborne transmission to the consumer population.
“While they are considered “last line of defense” drugs in human medicine, carbapenem antimicrobials are approved for use in food animal veterinary medicine. However, other beta-lactams are commonly used in almost food animal species worldwide, including ceftiofur and cefquinome extended-spectrum cephalosporin drugs,” Thomas E. Wittum, PhD, professor and Chair of veterinary preventive medicine at The Ohio State University, and colleagues wrote.
“If CRE are present in food animal populations, a large number of consumers may be exposed through the food chain, resulting in a critically important emerging food safety issue.”
To assess whether the presence of a carbapenem-resistant gene is present among animals raised for consumer food products in the U.S., the researchers collected fecal samples, fecal swabs, electrostatic clothes and sterile gauze from one 1,500-sow farrow-to-finish pig farm during four visits in July, August, October and November 2015. As per barn protocol, piglets routinely received prophylactic Excede (ceftiofur, Zoetis) treatment at first day of life, male pigs received prophylactic ceftiofur at castration (aged 5 to 7 days) and sows received therapeutic Excenel (ceftiofur, Zoetis) if affected by metritis and other bacterial infections.
To detect carbapenem-resistant isolate development from both environmental and fecal matter, the researchers incubated samples in combination with agar and biochemical assays overnight in a laboratory setting after each visit to the farm.
Laboratory analysis showed that of 30 environmental samples collected in the first visit, two (7%) samples produced three carbapenem isolates composed of Escherichia coli (n = 2) and Proteus mirabilis (n = 1), which both carried the metallo-beta-lactamase gene IMP-27 on IncQ1 plasmids. Further, the researchers detected 15 IMP-27 bearing isolates of several Enterobacteriaceae species from 11 of 24 (46%) environmental samples collected at third visit that also carried IMP-27 on IncQ1 plasmids.
Moreover, the researchers hypothesized the administration of ceftiofur to piglets only in the nursery and not in the farrowing process yielded the loss of the ecological niches necessary to maintain IMP-27.
“The implication of our finding is that there is a real risk that CRE may disseminate in food animal populations and eventually contaminate fresh retail meat products,” Wittum and colleagues wrote. “Foodborne transmission may then produce a reservoir of mobile carbapenemase genes in the enteric flora of consumers.” – by Kate Sherrer
Disclosure: This study was funded by The Ohio State University Public Health Preparedness for Infectious Disease Program and the USDA NIFA award #2014-67005-21709.
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