Researchers use water troughs to monitor resistant bacteria and help decide which antibiotics should be administered
Researchers are seeking ways to manage antimicrobial-resistant bacteria on farms, including quicker evaluation of bacteria so treatment can be better targeted.
Agriculture Canada and University of Saskatchewan veterinary school researchers are studying feedlot water troughs, hoping the water can tell them what sort of anti-microbial resistant bacteria are present.
“By knowing what type of resistance is there, we would avoid the use of antibiotics that those resistance genes confer resistance to,” says Dr. Trevor Alexander, research scientist with Agriculture Canada.
Burgeoning anti-microbial resistance on Canadian farms makes infections more difficult to treat.
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In 2010, a research project run by Tim McAllister at Agriculture Canada showed that about 10 percent of the mannheimia haemolytica bacteria studied on farms were resistant. Mannheimia haemolytica is the most common cause of bovine respiratory disease in beef cattle.
About six years later, a follow up study conducted with Edouard Timsit at the University of Calgary found about 70 percent of bacteria of concern were resistant to antimicrobials.
Antimicrobial resistance grows when antibiotics are repeatedly used on the same farm and the susceptible bacteria are killed, leaving larger numbers of bacteria resistant to that drug.
Research projects around the world are studying how farm management can help reduce such resistance.
Quick testing to determine levels of resistance and identify bacteria that are causing an infection could lead to better treatment decisions.
Alexander, based in Lethbridge, worked with Dr. Murray Jelinski at the Western College of Veterinary Medicine at the University of Saskatchewan to evaluate bacteria in water bowls in feedlots as a way to monitor for and manage antimicrobial resistance.
They took water from feedlot water bowls and tried to grow mannheimia, histophilus and pasteurella in the water.
Water bowls were chosen because they are visited by all animals in a pen and cattle will stick their noses into the water while drinking, passing bacteria. A nasal swab is now the only effective way to track respiratory disease bacteria in cattle. That process involves a lot of individual work with cattle.
A water-based test would be a more efficient way to understand the resistant bacteria types that are circulating among cattle in the pen.
“We saw that the survivability was really quite low for histophilus. More than 90 percent of the bacteria died within 24 hours,” says Alexander.
There were few remaining after three days. That means the test had to be done quicker.
Researchers worked with another feedlot and tested bacteria the same day. That resulted in some isolation of pasteurella, but not histophilus or mannheimia.
“So those bugs are tricky,” says Alexander. “The methods today, we don’t have a really great method to isolate those bacteria. We don’t have highly selective media to isolate those bacteria.”
They looked at how some bacteria were related and concluded that some were cloned in the pen, meaning they were being passed, likely through water. Researchers are now using metagenomics, the genome analysis of material in a sample from the environment, in this case a water bowl in a pen of cattle, to be sure that the bacteria were passed between cattle through the water.
This won’t help identify specific resistance within the genomes of bovine respiratory disease-resistant bacteria, but “we can look at all the resistance genes there and get a good idea of what we already know about resistance in feedlot pens,” says Alexander.
“Once animals come into the pens and the pen density is high, and then they’re sharing water at the water troughs, we do see an increase in the prevalence of BRD pathogens.”
He says there are many good reasons to keep troughs clean but there are no studies on how often they should be cleaned and how much treatment would reduce pathogen spread.
Other projects in Canada are looking at mobile elements in resistant bacteria that result in spread, and the use of long-read sequencing, a newer type of genetic analysis that could result in quicker, more accurate results of the type of BRD bacteria in a sample from a nasal swab.
