Has Last Shoe Dropped in Fight Against Superbugs?

Underscoring the potential public health threats widespread agricultural practices pose, bacteria resistant to a class of last-resort antibiotics known as carbapenems has for the first time been found on a U.S. pig farm.

The findings were published Monday in Antimicrobial Agents and Chemotherapy, a journal of the American Society for Microbiology, and come just months after another antibiotic used as a last resort—colistin—was found in a pig in the U.S.

The Centers for Disease Control and Prevention has said Carbapenem-resistant Enterobacteriaceae (CREs), which are carried by a mobile piece of independent DNA called a plasmid, present an urgent public heath threat.

“It’s a surprise that they would show up in livestock,” said corresponding author, Thomas Wittum, professor and chair of Veterinary Preventive Medicine at Ohio State University.

An accompanying press statement notes that “[c]arbapenems are a subset of β-lactam antibiotics. Β-lactam antibiotics which are not carbapenems are legal for use on farms in the U.S.”

For the study, researchers took environmental and fecal samples during four visits over a five-month period from a 1,500-sow, farrow-to-finish pig farm which “followed typical U.S. production practices.” Piglets in the farrowing area are given a dose of Ceftiofur—a β-lactam antibiotic—with males given a second dose.

The researchers said they were surprised at finding the few samples of the resistant gene, as it’s a closed barn—no new animals had been introduced for five decades. So how did it get there? “We don’t know,” Wittum told HealthDay News.

Wittum added that the researchers found “no evidence the pigs carried the gene into the [human] food supply.”