Their impact in poultry and an investigation of the relationship between virulence and antimicrobial resistance in Salmonella and Campylobacter isolates
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| Anne Letellier of the Université de Montréal set out to determine if certain farming practices, especially the use of antimicrobial agents, affects the presence of C. jejuni and Salmonella as well as their antimicrobial resistance profiles.
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Campylobacter jejuni and Salmonella spp. are leading causes of foodborne enteric diseases in humans and poultry products are a major vector of infection. In poultry production, the factors related to C. jejuni and Salmonella presence and persistence in birds are poorly understood and need to be identified in order to reduce or eliminate these pathogens at the farm level.
The use of antimicrobial compounds, either as growth promoters or as therapeutic agents, has raised concerns for the consumer mainly due to the potential for development of antimicrobial resistant bacteria. It has also been demonstrated that some Salmonella isolates carry genes providing resistance to some disinfecting agents that are cross-linked with antibiotic resistance determinants. For C. jejuni, this remains to be confirmed.
With this in mind, Anne Letellier of the Université de Montréal, set out to determine if certain farming practices, especially the use of antimicrobial agents, affects the presence of C. jejuni and Salmonella as well as their antimicrobial resistance profiles. At the end of summer 2008, Letellier and her research team sampled birds from 54 farms at the slaughterhouse. Each participating poultry producer completed a short survey covering specific farming practices as well as which antimicrobials were used during rearing of the birds.
Their findings? For C. jejuni, 19 per cent of the sampled farms were positive. It was found that complete disinfection of the farm, use of a surface well as water source, use of bacitracin, and chlorination of water at five parts per million raised the chances of isolating C. jejuni. Partial disinfection of the farm, use of clopidol, use of 3-nitro, and chlorination of water at three parts per million lowered the chances of finding this bacteria in the birds. Antimicrobial resistance was found to be low within the isolated C. jejuni.
For Salmonella, 64 per cent of farms were positive. Several serogroups were found to colonize the chickens, with S. Heidelberg being the most predominant strain. It was found that complete disinfection and use of Zoalene increased chances of Salmonella isolation while removal of dust (as the only cleaning method), use of Clopidol and use of quaternary ammoniums as disinfectant decreased that chance. Work is still underway to characterize the antimicrobial resistance profile of the isolates.
Overall, farming practices seem to be important for the control of Salmonella and C. jejuni at the farm. Care should be taken when interpreting the finding that complete disinfection increases chances of isolation of these pathogens, as not all farming practices were covered in this study.
However, it may be that complete disinfection offsets the natural balance of competitive microflora, creating an opportunity for growth of Salmonella and C. jejuni. Complete disinfection may give a false sense of confidence, and biosecurity measures should always be respected, even if the farm has been thoroughly cleaned. For more information on this study, please visit www.poultryindustrycouncil.ca and go to Research.
PIC PICKS
Science in the Pub just keeps getting better! Over 60 people turned up at the eBar in Guelph Jan. 12 to listen, debate, and discuss the thorny issue of laying hen housing.
Superbly moderated by Dr. John Kelly, the evening kicked off with a no-holds-barred presentation from Dr. Ian Duncan (University of Guelph) on why conventional cages are bad for bird welfare. During his presentation, he acknowledged the intrinsic benefits of caged systems, but the discomfort in the room was palpable when Dr. Duncan suggested that the birds in conventional cages suffer and that cage systems have led to a situation wherein egg producers no longer make daily checks on their birds but simply rely on a “sniff test” to locate and remove dead birds. He produced a plethora of science to back up most of his assertions (the “sniff test” not being one of them) and in doing so, seriously challenged the panel and audience to debate him.
The ensuing discussion was robust and the producers present gave good account of their practices. Audience and panel members, particularly Dr. Michelle Guerin (University of Guelph), offered up some equally valid points relating to the welfare inadequacies of the alternative systems, including bone breakages and internal and external parasites. The end point was a general agreement that, as of yet, there is no perfect system and it was hoped the colony systems, which are still very much in their infancy and under development, will provide a “best of both worlds” approach.
Dr. Tina Widowski (also of the University of Guelph) took a different approach and explained some of the mystery surrounding opinion poll results relating to animal welfare and how they do not translate into buying habits at the checkout counter. This was new work that she had undertaken and she told us that we all have a “citizen” personality and a “look after number one” personality. This Jekyll and Hyde problem manifests itself as follows: When, for example, we are asked if we prefer a Porsche to a second-hand Volkswagen, most of us would say we want the Porsche. But faced with the decision to buy one, most of us would be forced to choose the “VW” because of other external (usually financial) constraints.
It seems that this behaviour also applies to the question of animal welfare. If we’re surveyed while going into a supermarket, most of us want animals to have what we would think of as perfect living conditions; however, it appears that even when we’ve said minutes earlier in the survey that we’ll pay more for eggs from what the general public would consider a more welfare-friendly environment, we don’t pay more. At the supermarket we choose with our wallets.
Gail Campbell (Consumers Council of Canada) supported this notion, verifying that consumers’ main interests were food safety, quality and price, with little thought of how the food is produced. She believes this opinion is due to the fact that consumers have an inherent belief and trust in the manufacturer/producer of the product.
Harry Pelissero (Egg Farmers of Ontario) provided some very good information on European attitudes and the problems being faced by the Californian legislature in light of the inadequacies of Proposition 2, which passed last year and will see Californian Egg producers bear the high costs of abiding by the regulation, and potentially face a market that could be unfairly tipped against them as more cheaply produced eggs flow into the state from elsewhere.
Craig Hunter (Burnbrae Farms), an egg farmer for (by his calculation – if he really started at age three) over 60 years, had some wise words about meeting market demand and ensuring that farm practices meet accepted welfare standards. He said that a certain level of transparency in a farming system is a good thing to ensure that those who are really interested – and it’s not the vast majority – can see and understand where their food comes from.
In fact, that was how the evening ended – with the conclusion that producers will meet market demand for whatever the product is, egg marketers will promote the value of eggs of all shapes and sizes and production methods, consumers will continue to look for safe, quality, value-for-money food, and researchers will continue to work towards developing the “ultimate” system that meets the perceived needs of laying hens while retaining the high levels of productivity we enjoy today.
Which brings me to my final point. At the start of her talk Dr. Widowski posed the question, “Who is driving the change in housing systems?”, meaning is it industry, the market, lobby groups, etc.? I’m convinced it really matters who’s driving the changes because, ultimately, the bigger question concerning all of intensive livestock production is this: have those regulators who bring the changes into the legislation really discussed and debated the potential unintended consequences of the de-intensification of current livestock production systems for the economy, the environment and, most importantly, the world grain/food supply? We can only hope that they have, and that they have a “plan B,” or they may well find themselves with a human welfare problem with which to contend.
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