High doses of antibiotics in animal agriculture, as opposed to constant low doses, could be contributing to the growth of antibiotic resistant bacteria, according to a leading scientist on the subject.

On July 12, Dr. Randall Singer, a professor of epidemiology at the University of Minnesota, spoke about antibiotic resistance development at the Poultry Science Association's annual meeting in New Orleans at a symposium sponsored by Alltech. Singer, who’s served on national advisory boards focusing on the topic, said the poultry industry’s steady removal of antibiotic growth promoters could contribute to the development of antibiotic resistant microbes.

That result would be directly contrary to the goals of the U.S. Food and Drug Administration’s (FDA) forthcoming Veterinary Feed Directive (VFD), which will ban the use of growth promoting antibiotics the FDA deems medically important to humans in the U.S. The VFD, and similar measures around the world, are designed to protect antibiotics’ long-term effectiveness in human medicine. Singer said research suggests animal agriculture’s switch to using short, high doses of antibiotics to treat disease rather than constant, low doses of antibiotics to prevent disease could actually make the problem worse.

“If there is anyone in the room who still argues the way that we use antibiotics in poultry production does not have an impact on resistance or does not have an impact on human health, please stop,” Singer said. “All antibiotics have the potential to select for resistance.”

High doses could contribute to antibiotic resistance

Singer referenced studies that concluded the use of high doses of antibiotics, rather than constant low doses, could be encouraging the selection of antibiotic resistant bacteria. This is difficult in the poultry industry in particular because of the way antibiotics are administered. In the dairy industry, for example, a single sick cow is given antibiotics to treat disease. In poultry, the entire flock is given antibiotics through feed or the water supply, which can harm the helpful bacteria living in the animals and contribute to antibiotic resistance, because of the animals’ close proximity to one another.

Even as the industry adopts more antibiotic alternatives, he said, any substance with antimicrobial properties can lead to further selection of antimicrobial traits in bacteria.


Food safety concerns

Beyond fostering antimicrobial resistance, Singer said, removing antibiotic growth promoters, and just managing disease, will also create food safety issues. He said resistant bacteria can lead to greater bacterial contamination of meat inside poultry processing plants and give integrators more problems controlling microbes inside their plants.

Singer said the poultry industry must respond to these challenges by tracking the bugs – Salmonella, E. coli and Campylobacter – to know that the treatment actions are not actually making the health situation worse.

The industry must also stop being defensive about its use of antibiotics and become a leader in the responsible use of antibiotics. The industry must be certain that its disease control strategy is not making the situation worse for animal and human health.

Research funding needed

Finally, Singer said, the science to understand the relationship between antimicrobials and antibiotic resistance in animals needs additional funding. The federal government and other public sources don’t have the money to support the research, so other entities must step up to finance the science.

Fully understanding the issue will take time – Singer said the relationship between antimicrobials and antibiotic resistance took decades to develop – so the industry may not see a change overnight, but high dose therapy in the long run, may lead to serious problems, especially if the industry is not making an effort to monitor resistance.