Class of Antibiotics Used in Poultry May Contribute to Antimicrobial Resistance in Humans

New research suggests that “a class of antibiotics commonly used in poultry and other food-producing animals, but not in people, could contribute to antibiotic-resistant infections in humans.” CIDRAP has the news.

Ionophores, the antibiotic class in question, are “used to treat the parasitic infection coccidiosis in poultry and to promote growth and prevent disease in pigs and cattle. Ionophores are one of several classes of antibiotics used in food-animal production that are considered non-medically important because they aren't used in human medicine, due to toxicity.” A study revealed that “ionophore use could co-select for resistance to medically important antibiotics, such as tetracycline and vancomycin.” Senior author Alex Wong says that this “suggests that the assumption that ionophore use in animals is safe for humans is not a good assumption.”

The researchers examined genome sequence data for narA and narB genes, “which have been found to confer resistance to the ionophores narasin and salinomycin in Enterococcus faecium.” They found the genes present in 2,442 bacterial isolates from 51 countries; more than 500 of those isolates were collected from people, “a finding the researchers say indicates there's been some transfer from farm animals to humans.” The findings suggest that “continued ionophore use in food-animal production could not only select for more ionophore resistance, but also for resistance for antibiotics that are needed for human medicine.”

Wong also said that “there are several areas of research to pursue to further demonstrate human risk. One will be further molecular analysis to determine whether animal and human isolates carrying ionophore-resistance genes are closely related. He also wants to investigate transmission routes.”