OVC Researchers Study Manure Treatment Strategies To Reduce Resistant Bacteria

An ongoing research project co-led by researchers at the University of Guelph’s Ontario Veterinary College (OVC) is assessing manure treatments intended to prevent transmission of antibiotic-resistant bacteria. 

The team has found that anaerobic digestion – fermentation in the absence of oxygen – significantly reduces the frequency of bacteria resistant to several critically important antibiotics in manure used on farm fields, according to Dr. Patrick Boerlin, a professor in OVC’s Department of Pathobiology, and recent MSc graduate Rebecca Anderson.  

“We don’t want resistant bacteria to potentially end up in our food, possibly causing infectious bacteria to become resistant in our population,” said Boerlin. “The U of G team is continuing this research, to try to understand which treatment processes are most efficient at reducing the transmission of resistant bacteria to the end product of manure.” 

The U of G lab is co-leading assessment of dairy manure treatments in Canada under a European Joint Programming Initiative on Antimicrobial Resistance project coordinated by researchers in the Netherlands. Also co-leading this global One Health initiative is an Agriculture and Agri-Food Canada lab in London, Ont., led by principal research scientist Ed Topp.  

Other research teams on this project are investigating manure intervention strategies, such as treatments related to temperature change. Boerlin and Anderson focused on characterizing antibiotic-resistant bacteria recovered from the manure samples by assessing the frequency of resistant bacteria identified before, during and after treatment. 

They characterized resistant bacteria mostly using genome sequencing and bioinformatics, which is the collection and analysis of complex biological data. The aim: to trace bacteria and antibiotic-resistance genes through the varied manure treatment steps. 

The research team received manure samples from six farms across Southern Ontario through their London collaborators.  

The U of G researchers grew the bacteria and identified genes that make them resistant to antibiotics. Often, these genes are located on plasmids – small circular DNA strands – that help transmit antimicrobial resistance between unrelated bacteria. 

Studying antibiotic-resistant bacteria before and after manure treatments aids in understanding effective treatment strategies, which can lead to implementing appropriate techniques on a larger scale. 

Originally intended to be a three-year study, the project has been extended to early 2024 due to the COVID-19 pandemic. Dr. Nicole Ricker, in OVC’s Department of Pathobiology, is now taking the lead on the U of G portion of the project. 

“We are hopeful that our results will help bridge some gaps in this area of research, ultimately protecting both humans and animals in the long run from antibiotic-resistant bacterial infections,” said Anderson. “This is a complex One Health issue, and the problem goes both ways. Therefore, focusing on antimicrobial resistant bacteria before they enter the food chain is a good place to start.” 

Funded by the Canadian Institutes of Health Research, this project also involves collaborations with Dr Michael Mulvey and his team at the National Microbiology Laboratory in Winnipeg.