Threatening drug resistance gene found on swine farm

Environmental samples from a U.S. swine farm contained several species of Enterobacteriaceae with carbapenem resistance genes that could be transmitted to other bacteria, a scientific article states.

The article authors, a team from The Ohio State University, wrote that the carbapenem-resistant species of Enterobacteriaceae—such as Escherichia coli and Proteus mirabilis—found in a swine farrowing barn are the first discovered in U.S. livestock to carry the resistance genes on a transmissible plasmid.

The article, published Dec. 5, 2016, in Antimicrobial Agents and Chemotherapy, the American Society for Microbiology’s online-only journal, notes that a separate scientific article published in January 2016 described discovery of carbapenem-resistant and carbapenemase-producing bacteria, including species of Enterobacteriaceae, in U.S. dairy cattle. While isolates found in those dairy cattle could transmit resistance genes only to daughter cells, those found on the swine farm are more substantial threats to public health because of their potential for transmission between commensal bacteria and pathogens.

A related announcement from OSU indicates the resistance gene likely was brought onto the farm through an outside source, but use of the antimicrobial ceftiofur in the farrowing barn may have provided selection pressure to help it spread. The scientific article states that pigs in the farrowing barn often receive ceftiofur within the first week of life, and pigs in the nursery and finishing barns receive occasional therapeutic doses.

Information from the Centers for Disease Control and Prevention describes carbapenem-resistant species of Enterobacteriaceae as highly resistant, difficult-to-treat emerging public health threats.

The Ohio State announcement indicates the research team found no evidence carbapenem-resistant species of Enterobacteriaceae or the genes conveying resistance were carried by the farm’s pigs into the food supply.