Campylobacter jejuni in chickens at slaughter and retail Dr. M. VanderKop Head, Surveillance Project Systems Section Food Safety Division Alberta Agriculture, Food and Rural Development

Abstract:

Campylobacter jejuni is the leading confirmed cause of acute gastroenteritis in people, causing a self-limiting diarrhea or dysentery. In many cases the infection is associated with consumption of poultry products or cross contamination by raw poultry. The bacteria are commonly shed in the feces of chickens and spread rapidly between birds. There have been many studies of risk factors for infection without clear conclusions, and some of these recommendations will be discussed.

Campylobacter spp. develop resistance to antibiotics very readily and use of fluoroquinolone antibiotics in livestock has been implicated as a source of resistance of strains of Campylobacter spp. in human infections. It is important to examine the level of resistance to establish baselines and determine whether there has been an impact from current use of these antibiotics in Alberta.

The objectives of this work were 1) to determine the baseline level of Campylobacter spp. in Alberta broilers and retail chicken through a representative sample, 2) to establish whether the strains of Campylobacter spp. isolated from birds at slaughter were the same as those seen in whole retail chicken, based on pulsed field gel electrophoresis patterns and 3) to establish and compare resistance patterns to fluoroquinolone antibiotics.

Campylobacter jejuni was found in 35% of broilers at slaughter, with equal proportions from birds presenting to major processors. Only 12% of these isolates were resistant to enrofloxacin, with a higher proportion of resistance found in birds from one processing plant, perhaps reflecting different flock management recommendations. Whole body wash of retail chickens had C. jejuni recovered from 53% of samples and 12% of these samples were resistant to enrofloxacin. These did not differ in distribution between Edmonton and Calgary. There have been no differences detected between the retail and slaughter samples by pulsed field gel electrophoresis, but further analysis is underway. There were small numbers of C. lari isolated from retail samples only, not from any chicken samples.

Campylobacter spp. in Chickens - Prevalence and Antibiotic Resistance

Poultry Service Industry Workshop
October 2002
M. VanderKop, Marg McFall, Ole Sorensen

Campylobacter jejuni is the leading confirmed cause of acute gastroenteritis in people, resulting in a self-limiting diarrhea or dysentery. There are estimated to be 8-15 cases per 100,000 people annually, but it is suspected that many cases are so mild that they are not reported (Tauxe 1992). The clinical disease is often associated with consumption of food contaminated by juices of raw poultry or with eating undercooked chicken (Bryan and Doyle 1995, Aletkruse et al 1999). Occasional outbreaks have occurred due contamination of milk or water sources. While Campylobacter accounts for only 12% of food borne illness fatalities (Meer and Misner 1998), the bacteria can survive processing and chicken is frequently associated with infection so it is important to have an understanding of the prevalence of these bacteria in poultry populations and to monitor these levels to establish whether control programs are effective.

The issue of antimicrobial resistance has emerged with Campylobacter species since they develop resistance relatively readily and rapidly. Fluroquinolone resistant strains have been detected in Europe and the United States and associated with the use of these antibiotics, like enrofloxacin, in poultry and other livestock species (McClellan et al 2002). There are concerns over human health, because if bacteria become resistant to drugs used to treat human infections, those drugs may not be effective for treatment. Of even more concern is that the resistance that is developed will be transferred to other, more pathogenic bacteria. These concerns have led to the withdrawal of certain anitibiotics from the market, which has an impact on the ability of livestock producers to medicate stock.

Campylobacter is an unlikely pathogen - it has very specialized growth requirements and is very sensitive to environmental challenges. It requires an atmosphere with reduced oxygen and temperatures of 42-43 degrees C in order to grow. It is killed readily by drying, acidity, salt, and osmotic gradients, but still accounts for a large number of human infections, likely because if its ability to survive in a liquid environment. The infective dose is also very low, with fewer than 1000 organisms required to produce infection in a person. As few as 50 bacteria can colonize a chicken, and this accounts for rapid spread in infected barns Berndtson et al 1996, Jacobs-Reitsma et al 1994).

Campylobacter has been cultured at rates between 35-90% in poultry, both in individual birds and flocks studied ( Berndtson et al 1996, Jacobs-Reitsma et al 1994, Altekruse et al 1999). It resides in the mucus layer in the cecum portion of the large intestine and is spread through feces. While Campylobacter does not produce clinical signs in poultry so is not a concern for producers related to bird health, it remains an important contaminant of chicken meat. When birds are stressed and closely packed during transport, fecal contamination of the skin can occur and the bacteria are retained within skin pores. This can result in cross-contamination between infected and clean birds, which is possible in chill tanks. Surveys have detected Campylobacter in up to 90% of retail chicken samples, which means it is a major customer concern (Powell et al 1995). While it is killed by cooking, consumers expect to be assured that such contaminants are not present in their foods.

Numerous studies have been conducted to establish which on farm management factors are important risks for Campylobacter infection in a flock. Infection is rare in birds under 2 weeks of age and egg transmission has not been substantiated. It has not been possible to establish infection in fertile eggs and Campylobacter has rarely been isolated from them (Jacobs-Reitsma 1995, Kapperud et al 1993). Water, feed and litter have not been confirmed as sources and the most likely means of infection is contamination from infected birds or animals. There have been some associations of poultry infection with the presence of other livestock on the farm. Large numbers of bacteria are shed in feces, and tracking wet bedding and fecal material into barns is the most likely source of infection. Certainly lax biosecurity will permit entry of the bacteria into a flock and once it has infected a flock, virtually the entire barn will be positive by 6 weeks of age.

A study was designed to measure the level of Campylobacter in broilers arriving at slaughter and in whole retail chickens in Alberta grocery stores. The goal was to have a baseline for future monitoring as well as to establish which pulsed field gel electrophoresis types were present in these two populations and whether a relationship between the two could be established. Because antimicrobial resistance was an emerging issue, it was also desirable to investigate resistance patterns of these isolates, to fluroquinolone antibiotics used in livestock and erythromycin, which is the most commonly used treatment for human cases of Campylobacter.

The research design was a cross sectional study of a sample that would represent the Alberta broiler population. We estimated that approximately 6 million birds every 8 weeks were processed in four federally inspected plants. Ideally birds could be sampled on the farms and we could follow the same bird from placement through slaughter to retail, but practical limitations dictated that sampling take place at slaughter plants. A sample of 400 birds gives 95% confidence that the prevalence estimate will be accurate within 5%. The sample of 400 was allocated according to plant slaughter volume estimates and resulted in collecting cecal samples from 64 birds each at the smaller two plants and from 136 birds at the two larger plants. Samples could not be obtained in a true random fashion due to operational constraints, such as requiring transportation of samples to Edmonton for culture. Without true random sampling there are many possible biases, but we believe this was as representative a sample as could be practically obtained.

Retail sampling was done in Edmonton and Calgary based on their population and in Lethbridge because the laboratory has staff in Lethbridge to handle sample collection. A total of 400 whole, fresh, never frozen chickens were purchased from a random sample of 50 major groceries in each of Calgary and Edmonton. Two birds were randomly selected from each store on each of two visits. This sample size gave us similar confidence that our prevalence estimate would be accurate to within 5% of the true prevalence. The date, brand name and store source were recorded for comparison and to determine whether the sample was representative.

Both cecal samples and whole carcass chicken washes were cultured by direct and enrichment pathways to enhance isolation rates for Campylobacter. Antibiotic sensitivity was performed to determine the minimum inhibitory concentrations for three fluroquinolones (naladixic acid, ciproflaxacin and enrofloxacin) and erythromycin. Isolates were confirmed by polymerase chain reaction DNA testing. Pulsed field gel electrophoresis was completed to determine patterns that could be compared between retail and cecal samples.

Of the slaughter samples, 60.8% were negative culture, and C. jejuni was isolated from 35% of samples, with the remainder consisting of C. coli and C. lari. By comparison, retail samples had only 39.8% negative culture, with C. jejuni isolated in 53% of samples and C. coli and C. lari in the remainder. The distribution of isolates among the four processing plants and between the major cities did not differ, although the sample sizes were not established to provide sufficient power to support significant comparisons. These levels are lower than most reported prevalences, even for a sample taken during the winter months, when prevalence is typically lowest.

The C. jejuni isolated from slaughter samples showed 12.9% resistance to enrofloxacin, and those from retail samples were 12.2% resistant. There were not sufficient isolates of C. coli or C. lari to make meaningful comparisons. The slaughter samples were separated by processing plant and one plant showed a much higher proportion of isolates that were resistant to enrofloxacin but it was one of the smaller plants. This might reflect different management practices in different locations through the province, but without information on use of enrofloxacin the poultry flocks, it is not possible to draw firm conclusions.

The level of Campylobacter detected in Alberta slaughter and retail chicken is lower than that reported by many other studies. Resistance levels of only 12% are also quite low, but it is important to continue monitoring to determine whether these are maintained over time. Control measures that may be helpful on farm are focused on biosecurity - keeping traffic into barns to a minimum and controlling pests like rodents and wild birds that may carry infection. Once Campylobacter gains entrance to a barn, it spreads rapidly, so it is critical to keep it out. Controls at processing include air chilling, irradiation, and avoiding cross contamination through water.

In conclusion, we now have a better understanding of the Alberta situation with respect to Campylobacter, but need to continue to monitor. This monitoring could be part of on farm food safety programs, as a means of establishing whether or not control measures on farm are effective in reducing contamination in the final retail product.

Acknowledgements

Lilydale Cooperative and Maple Leaf processors for their cooperation in sampling.

Alberta Agriculture, Food and Rural Development, Food Safety Division, Agri-Food Surveillance Systems Branch and Agri-Food Laboratories Branch for funding this work.

Agri-Food Laboratories Branch for completing all the isolation and typing of isolates with special thanks to Arlene Otto, Carol Goertz, Sonja Marshall and Robin King.

Agri-Food Surveillance Systems Branch for performing all sample collection, with special thanks to Annette Visser, Chris Wilke and Laurie Reay.

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