National Pork
Ohio State University research study detailed discovery in one farrowing barn.

DES MOINES, Iowa – The discovery of a multidrug-resistant gene on a farrowing farm in the United States indicates that internal biosecurity measures at the farm are effective, the National Pork Board (NPB) said in response to a study detailing the finding made by researchers from The Ohio State Univ., Columbus.

In a statement, the NPB said the resistant gene identified in the study was not found in a market hog, and there was no threat to food safety.

“The US pork industry supports efforts to monitor for the occurrence of this type of isolated incident,” NPB said. “However, consistent with FDA and Pork Quality Assurance Plus requirements, Ceftiofur should only be used in the treatment and control of disease with veterinarian oversight and direction.”

The research was published in the journal Antimicrobial Agents and Chemotherapy by Thomas Wittum, chair and professor of the Dept. of Veterinary Preventive Medicine at OSU and several colleagues. The discovery is concerning because carbapenem antimicrobials are used in hospitals to treat infections caused by multidrug-resistant bacteria. Their use is not approved for food-producing animals. However, carbapenems belong to a class of broad-spectrum antibiotics called beta lactams; and other beta lactams, such as Ceftiofur and Cefquinome, are commonly used in food-animal production.

“While the exact relationship between extended-spectrum cephalosporin use and carbapenem resistance has not yet been established, use of these drugs is likely to provide significant selection pressure favoring organisms expressing carbapenem resistance because they will also be resistant to all extended-spectrum cephalosporins,” researchers said. “While most people today do not have direct livestock exposure, enteric flora from livestock commonly contaminate fresh retail meat products that are distributed over wide geographic areas. Thus, if CRE are present in food animal populations, a large number of consumers may be exposed through the food chain, resulting in a critically important emerging food safety issue.”

As part of the study, researchers collected environmental and fecal samples at a 1,500 sow, farrow-to-finish farm during four visits over a five-month period in 2015. The samples were screened “using selective media” for the presence of carbapenem-resistant Enterobacterioaceae (CRE). Analysis of the samples revealed the presence of a carbapenem-resistant gene called blaIMP-27.

Carbapenem-resistance has been found in livestock in Europe and Asia, it had not been identified in the US until the OSU study.

NPB noted that swine producers in many states voluntarily participate in The Ohio State Univ. Public Health Preparedness for Infectious Diseases Program which aims at better understanding emerging disease issues. NPB said more studies are needed to validate and replicate the finding.

“As experts in swine production, the Pork Checkoff is eager to analyze the initial findings, alongside its authors, and better understand results of this report from this farm,” NPB said. “Specifically, resistant gene samples were found in one barn, on one site without any confirmed indication of how the resistant gene got there.

“Ohio State University researchers acknowledge that it is unknown how the carbapenem-resistant Enterobacteriaceae (CRE) bacteria was introduced to the facility and that it could have been introduced by an outside source,” NPB added. “The conclusions drawn without further validation, replication and research demonstrate this issue requires additional study.”

The Atlanta-based Centers for Disease Control and Prevention (CDC) said CRE infections usually occur in hospitals, nursing homes and other healthcare settings. Healthy people usually don’t become infected. In its 2013 report on antibiotic resistance threats, the CDC estimated that CRE caused 9,300 infections and killed more than 600 Americans each year.