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Tracing-back Campylobacter

Though these bacteria are often associated with poultry, do Campylobacter in the beef sector pose an equal or greater food safety threat? A new study aims to find out.

Dr. Doug Inglis and technician Kathaleen House.

Do Campylobacter bacteria shed by cattle pose a threat to human health? That's an important, but complex question scientists from several Canadian research centres hope to sort out in new research over the next four years.

The research will track the Campylobacter species (i.e., campylobacters), a group of bacteria that are commonly shed in cattle faeces, says lead researcher Dr. Doug Inglis of Agriculture and Agri-Food Canada‚s (AAFC) Lethbridge Research Centre.

"The health risk that these bacteria represent to humans ingesting contaminated beef or water is currently uncertain," he says. "But, in light of increasing evidence implicating cattle as a source of the infectious bacteria, the new study aims to determine the risk to humans represented by several microorganisms, including Campylobacter, originating from beef cattle. Currently, poultry are thought to be the primary reservoir of Campylobacter species infecting humans. However there are strong indications that cattle are a major source as well."

For the past few years, Inglis and his Lethbridge research team have focussed efforts on Campylobacter, a family of bacteria that contains species known to cause acute diarrhea in humans throughout the world. The team has been involved in quantifying the species of bacteria shed in cattle manure, and they have also determined where these bacteria live in the intestines of beef cattle.

In related research, Inglis found feedlot cattle routinely treated with antibiotics shed Campylobacter bacteria possessing resistance to these drugs. These bacteria, known as antimicrobial resistant (AMR) bacteria, may survive in the manure, but it's not known if they can be transmitted to humans.

Human impact

"Considering the widespread use of antibiotics in cattle production and high frequency of beef cattle that shed campylobacters, it is important that we continue to monitor the development of antimicrobial resistance in Campylobacter feedlot cattle," he says. "The question we really need to answer is, what risk do AMR bacteria from cattle represent to humans?"

While the human health risk from other bacteria such as E. coli is a familiar to most people, Inglis says the lesser known Campylobacter might pose an even greater threat.

"Ignoring the contamination of food and water by Campylobacter and other human-pathogenic bacteria from cattle, and the adverse impact that they could have on humans would in all likelihood severely damage public confidence in the safety of Canadian beef," says Inglis. "We feel that campylobacters from beef cattle is an emerging issue that we have the opportunity to address in a proactive manner."

Working with colleague Dr. Tim McAllister, also of AAFC Lethbridge, the multi-institutional study will measure the occurrence and transmission of bacteria from beef cattle along the entire beef production chain from farm to food. "The overall goal is to determine if in-feed administration of antibiotics to feedlot cattle poses a significant risk to humans," says Inglis. "Although a logistically demanding project, the information obtained in this study should shed light on this important issue."

Cattle source

Campylobacter species, particularly Campylobacter jejuni and C. coli, are recognized as one of the most common causes of acute diarrheal disease (campylobacteriosis) in humans throughout the world, including in Canada, says Inglis.

Research investigating Campylobacter species associated with cattle in Canada has been relatively limited, says Inglis. However, a cattle source was implicated in the infection of many people in Walkerton, Ontario, by C. jejuni in 2000, and cattle have also been implicated as a source of the pathogen infecting humans in Europe. „Add to this, the high prevalence of campylobacteriosis in the Chinook Health Region of Southern Alberta, coupled with high densities of cattle in this region and it all suggests that cattle serve as a reservoir of human-pathogenic campylobacters," he says.

Initially, Inglis and his team that included technicians Kathaleen House, Jenny Gusse and Hilma Busz; doctoral student, Lisa Kalischuk; and undergraduate student Jennilee Jamison, set out to determine the relative abundance of different Campylobacter species shed in cattle faeces.

Tough to research

Campylobacters are very difficult bacteria to grow and this necessitated the development of new methods to accurately detect and quantify them. The LRC project developed a number of methods utilizing polymerase chain reaction (PCR), a method used to measure DNA from the bacteria.

Using PCR methods, Inglis‚ research showed more than 80 percent of faecal samples collected from approximately 400 beef cattle contained campylobacters; the two most prevalent species were C. jejuni and C. lanienae, but other species including C. coli, C. hyointestinalis, and C. fetus also were detected. The presence of C. lanienae was unexpected. This was the first study to report this bacterium from cattle.

The testing methods we developed were substantially more effective in detecting Campylobacter species than conventional culturing methods," says Inglis. "These methods are instrumental in developing and assessing control strategies, a primary focus of our current research at Lethbridge."

In addition to investigating human health aspects, Inglis' research will also determine if Campylobacter species, such as C. jejuni and C. lanienae, have an impact on cattle health. The bacteria can cause illness in young calves, but the impact on older cattle is unknown. "We are examining whether campylobacters are pathogens of cattle themselves," says Inglis.

We are taking a physiological and molecular approach to determine how Campylobacter causes disease in animals such as cattle, and this work is integrated with our research on antibiotic use in cattle, development of antimicrobial resistance, and our search for alternatives to antibiotics."

The safety of Canada's meat supply influences the competitiveness of the livestock sector both nationally and internationally, he points out.

"Canadian beef production relies heavily on confined feeding operations for the efficient and economical production of beef," says Inglis. "This mode of production is vital to the economy of the country. However, confined feeding operations are facing growing criticisms regarding food safety and environmental contamination. In addition to the potential health risk posed by human-pathogenic bacteria such as campylobacters that contaminate foods and water, another major concern is the development of antimicrobial resistance resulting from the use of antibiotics in cattle production.

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