New scientific research shows that two macrolide animal antibiotics, tylosin and tilmicosin, is safe and won’t harm the nation’s food supply. The findings were reported in the peer-reviewed publication, the Journal of Food Protection.

"We found that there is an extremely low risk of a person eating beef, poultry or pork and acquiring a resistant infection that is untreatable with a human macrolide antibiotic," says lead author H. Scott Hurd, veterinarian, Hurd-Health Consulting, Roland, Iowa.

The study assessed two bacteria, which are known to have resistance to certain antibiotics, and developed a mathematical equation to determine if using these two macrolide antibiotics could lead to foodborne infections in humans that are difficult to treat.

The results of the study, which was conducted by Hurd and a number of independent experts, show that the risk of acquiring a resistant Campylobacter infection from beef, pork, or poultry that results in a difficult-to-treat foodborne illness is less than one in 10 million. For resistant Enterococci faecium, the chances are even lower — less than one in three billion.

"Given these results, and the fact that human macrolide antibiotics are rarely used to treat people who have foodborne infections, macrolides certainly are among the safest for use in food animal production," says co-author Ronald N. Jones, The Jones Group/JMI Labs, North Liberty, Iowa.

"Antibiotic risks associated with other infectious diseases, such as pneumonia or bronchitis, are infinitely higher than for macrolide-resistant bacteria that could be acquired from food," he adds.

Jones says that antibiotic resistance efforts should focus on decreasing misuse of human antibiotics, such as prescribing them for colds and other viral infections that don’t respond to treatment with antibiotics.

The two macrolide antibiotics included in the study, tylosin and tilmicosin, are used in beef cattle to treat respiratory diseases and to prevent liver abscesses. They are used in poultry and swine to treat, prevent, and control diseases and for health maintenance.

The study, which was funded by Elanco Animal Health, was conducted using U.S. Food and Drug Administration risk assessment guidelines.

"Given the low probability of treatment failure as a result of eating meat or poultry from animals treated with these macrolide antibiotics, we concluded that using tylosin and tilmicosin in food animal production has a very low risk to human health," says Hurd.

The results were:

* Pork: The probability of acquiring a resistant infection from eating pork resulting in treatment failure is less than one out of 53 million people per year for resistant Campylobacter, and less than one out of 21 billion people per year for E. faecium.

* Beef: The probability of a resistant infection from eating beef resulting in treatment failure is less than one case in 236 million per year for resistant Campylobacter and less than one case in 29 billion per year for resistant E. faecium.

* Poultry: The probability of a resistant infection from eating poultry resulting in treatment failure is less than one case out of 14 million people per year for Campylobacter, and less than one in 3 billion people per year for E. faecium.

Other co-authors of the article include Stephanie Doores, Penn State University; Dermot Hayes, Iowa State University; John Maurer, University of Georgia; Alan Mathew, University of Tennessee; Peter Silley, MB Consult Limited; and Randall S. Singer, veterinarian, University of Minnesota.