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UCalgary researchers assess link between antimicrobial use and antibiotic resistance

Antibiotic resistance is a growing problem and is thought to be one of the biggest public health threats globally. While the issue has multiple contributors, the use of antibiotics in food animals and how that could translate to antimicrobial resistance in humans is of particular interest to a group of University of Calgary researchers, led by Dr. William Ghali, scientific director of the university’s O’Brien Institute for Public Health.

The team, which encompasses researchers from the Cumming School of Medicine and the Faculty of Veterinary Medicine, was recently selected by the World Health Organization (WHO) in a competitive global bidding process to conduct a systematic review of the available literature on the issue so as to inform the organization regarding the seriousness of the issue. The findings were presented to the WHO in October.

With a growing world population to feed, efficient animal production is a priority. While developed countries typically practise good hygiene and sound management, in developing countries, this is often lacking. As a result, the frequent use of antibiotics in these animals compensates for this poor management. The problem is, this can lead to antibiotic resistance.

“If a mutation occurs in the bacteria of an animal that is being treated, it can become resistant to that antibiotic and will continue to grow and reproduce in the animal,” says Dr. Herman Barkema of the Faculty of Veterinary Medicine and member of the O’Brien Institute for Public Health and Snyder Institute for Chronic Diseases. “Then you have people working with these animals; that are in direct contact with them: breathing the same air, touching their skin and fur, coming in contact with their waste. The idea is then that these people end up with more of the resistant bacteria as well.”

Antibiotic-resistant bacteria cannot be passed to humans through consumption of pasteurized or cooked animal products, such as milk and meat, because the bacteria are killed during the preparation processes. However, waste from these animals, which also harbors this bacteria, regularly gets into our lakes and rivers that supply our drinking water. The bacteria can then be passed on to humans.

One health

Animals and humans live together on the planet in an ecosystem that encompasses our waterways and vegetation. As up to 75 per cent of new infectious diseases in humans originate in animals, it’s important that we don’t treat these entities in isolation, but consider them all when establishing and implementing treatment protocols.

“When we treat animals with antibiotics, we aren’t just treating the bacteria in those animals,” says Barkema. “We are treating the microflora in the rivers, the fish and other aquatic life in those rivers, the other animals that drink from those rivers and the humans that get their drinking water from those rivers. We’re all very interconnected.”

Report findings

The report looked at 175 studies on the topic of antibiotic resistance in animals. Twenty one of those looked at antibiotic resistance in humans.

“Our findings suggest that interventions that reduce or restrict antibiotic intervention can reduce the risk of antibiotic resistance in animals and humans,” says Dr. Karen Tang, study co-author and a member of the university’s O’Brien Institute for Public Health. “There is a large body of evidence to suggest a direct link in animals between the use of antibiotics and antibiotic resistance. While in humans the body of evidence is smaller, due to fewer studies on the subject area being available, a definite link, albeit smaller, is still there.”

The findings from the report are clear that all interventions, regardless of the nature or capacity they are conducted in, have a positive influence on reducing the numbers of antibiotic resistant bacteria that are produced.

Current treatment protocols

With the exception of organic farms, most farms in North America will regularly treat their animals with low dose antibiotics. This treatment regime prevents diseases and promotes growth in the animals, thereby increasing the efficiency of animal production. Those animals that fall ill will be treated with higher doses of antibiotics; however, on organic farms, these animals will often be culled. 

The North American governments have banned the use of some antibiotics in animals that are vital in the treatment of some human diseases such as tuberculosis. This is done so as to prevent resistance to these drugs from occurring.

Impact from the WHO

While the focus of the report was on the use of antibiotics in food animals, the practice isn’t the only contributor to antibiotic resistance. For example, antibiotics are often overprescribed in Canada to humans, often for treatment of viral infections that will not be influenced by the medication.

“It has really been a tremendous experience for us working on this ambitious project, because it has given us an opportunity to work with the WHO and other global stakeholders on a health issue that has extremely broad and far-reaching implications,” says Ghali. “It has also been a tremendous experience for us within the University of Calgary community, because this work has strengthened exciting collaborative linkages between the Cumming School of Medicine and the Faculty of Veterinary Medicine. We look forward to many more interactions going forward."   

Dr. Bill Ghali is also a professor in the departments of medicine and community health sciences at the Cumming School of Medicine.

The Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases was named in 2008 in honour of Joan Snyder and her parents, who she credits for teaching her the value of philanthropy. It is a group of more than 104 clinicians, clinician-scientists and basic scientists who are impacting and changing the lives of people suffering from chronic diseases, including sepsis, MRSA, cystic fibrosis, type-1 diabetes, inflammatory bowel disease, and chronic obstructive pulmonary disease. For more information on the Snyder Institute for Chronic Diseases, please visit us at or follow us on Twitter @SnyderInstitute.