Bacterial Whack-a-Mole: Reconsidering the Public Health Relevance of Using Carbadox in Food Animals

Abstract

Carbadox is an antibiotic used to control dysentery and promote growth in swine in the United States; however, the drug also causes tumors and birth defects in laboratory animals. Despite this and because the drug has no analogs in human medicine, it is not considered “medically important” and can be used in livestock without veterinarian oversight. In their recent study, T. A. Johnson et al. (mBio 8:e00709-17, 2017, https://doi.org/10.1128/mBio.00709-17) demonstrated that carbadox has profound effects on the swine gut microbiome, including the induction of transducing phage carrying tetracycline, aminoglycoside, and beta-lactam resistance genes. In swine production, carbadox can be used in conjunction with other antibiotics (e.g., oxytetracycline) that could fuel the emergence of strains carrying phage-encoded resistance determinants. Johnson et al.’s findings underscore the potential unforeseen consequences of using antibiotics in livestock production and call into question our current methods for classifying whether or not a veterinary drug has relevance to human health.

Advances in Metabolism and Metabolic Toxicology of Quinoxaline 1,4-Di-N-oxides

“…coli infection in weaned piglets . Specially, CBX may contribute to the emergence of strains carrying phage-encoded resistance determinants clusters in combination with other antibiotics in growing livestock …”

“…23 Specially, CBX may contribute to the emergence of strains carrying phage-encoded resistance determinants clusters in combination with other antibiotics in growing livestock. 24 CBX could also induce bacteriophage-mediated gene transfer, leading antibiotic resistance genes into sensitive bacterial hosts. 25 With regard to the metabolites of CBX, Cb3 (bisdesoxycarbadox) was reported with mutagenic and chromosomal abnormal toxic effects both in vivo and in vitro in mice.…”