Researchers from North Carolina State University have found identical strains of antibiotic-resistant Campylobacter coli (C. coli) in both conventionally raised pigs and those raised without antibiotics. In the United States prophylactic use of antibiotics is legally and use of antibiotics at subtheraputic doses as growth promoters is widespread.

This finding may indicate that these antibiotic-resistant pathogens can persist and thrive in the environment, regardless of antimicrobial usage by pork producers, the researchers have said. Whilst these findings may serve to benefit the wealthy North American livestock and pharmaceutical lobbies, both of which are working hard to block moves within government to crack down on antibiotic use, the implications are concerning nonetheless.

Following moves in Europe, where the use of drugs as growth promoters is banned, to reduce antibiotic use in agriculture, United States government agencies are slowly working to reduce the misuse of and overreliance on antibiotics amid fears of growing resistance to these essential drugs.

Professor Siddhartha Thakur of the University of North Carolina found that antibiotic-resistant C. coli (campylobacter) a leading cause of foodborne illness, are present in both drug-free and conventionally raised pigs in the US. The ‘superbugs’ were present in both animals in all facilities from breeding to processing.

Thakur said, “The rise of antibiotic-resistant pathogens like C. coli is a concern for the food animal industry. Some pig farms have switched to raising ABF pigs in an attempt to get away from the conditions that facilitated antibiotic resistance in the first place. The hope is that once the selection pressure – in the form of antimicrobial use – on C. coli to retain antibiotic resistance decreases, the pathogen will lose its resistance.”

The North Carolina researchers concluded that the environment must be playing a large role in the continuing survival of antibiotic-resistant C. coli, as pigs from both systems which never came into contact were both found to carry antibiotic resistant bacteria.

Thakur's findings appear online in PLoS One.

"In the case of ABF pigs, the environment plays an important role in their exposure to these resistant strains," Thakur said. "If the environment itself, and not the pig, is serving as a reservoir for C. coli, then we will most probably continue to find resistant bacterial populations, regardless of a producer's antimicrobial use."

Thakur added that the diverse C. coli populations identified in the study are thought to share a common ancestry, which could potentially explain the high prevalence of antimicrobial resistant bugs in antibiotic-free systems examined in the absence of antimicrobial selection pressure.

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