National Microbiological Baseline Study in Broiler Chicken
December 2012 – December 2013
Executive summary
Food animals including avian species naturally carry pathogens in their intestinal tract that may be transferred on to raw meat products during slaughter and processing. The main objective of this microbiological baseline study was to provide national and current baseline estimates on the prevalence and concentration of Campylobacter and Salmonella in broiler chicken and chicken meat produced in Canada. This information will be used to assess risk management programs including the potential setting of pathogen reduction targets or performance standards.
The design of this study follows a unique farm-to-retail approach to provide baseline data at the farm, processing and retail level. This approach is intended to allow governments and industry to evaluate the effects of current and future interventions at all stages along the food chain.
The detection and enumeration of Salmonella, Campylobacter, and generic E. coli in various sample matrices was performed by an accredited third-party laboratory using United States Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) methods. All bacterial isolates recovered from positive samples are being characterized by PHAC and CFIA laboratories using reference phenotyping and genotyping methods.
The prevalence estimates presented in this report are not fully weighted and thus not considered as the final national prevalence estimates. The statistical process of weighting or applying the appropriate weight to each primary sampling unit will be performed and reported at a later stage to derive more precise estimates. The reported prevalence of Campylobacter on fresh abattoir and retail chicken products was estimated by combining the results of both qualitative and quantitative tests.
The farm component was assessed through the collection and testing of caecal contents of chicken carcasses at slaughter which reflects the contamination status of the flock. A pooled caeca sample was collected from a set of 20 individual birds of the same lot or truck load at slaughter to estimate the prevalence of these foodborne pathogens in flocks and farms. The results of this study show that the prevalence of Campylobacter and Salmonella in broiler chicken lots raised on Canadian farms vary widely over seasons and provinces.
The national prevalence of Salmonella in broiler chicken lots was 25.6% (CI: 24.3% – 26.9%). The lots raised in eastern provinces were colonized more frequently with Salmonella with Ontario demonstrated the highest prevalence with 34.3% (CI: 31.4% – 37.2%). The national prevalence of Campylobacter in broiler chicken lots was 24.1% (CI: 22.8% – 25.4%), but the geographical distribution of positive lots increased gradually towards the west with British Columbia showing the highest prevalence at 41.3% (CI: 37.7% – 44.9%).
The prevalence of Salmonella on whole carcasses and parts processed in federally-registered establishments were significantly different at 16.9% (CI: 15.1% – 18.7%) and 29.6% (CI: 27.4% – 31.7%), respectively. Similarly, the prevalence of Campylobacter was significantly lower on whole carcasses at 27.4% (CI: 25.2% – 29.6%), compared to parts at 39.0% (CI: 36.7% – 41.4%). When analyzed separately, the prevalence of both pathogens in skinless and boneless (SLBL) breasts was not significantly different from the prevalence observed on skin-on and bone-in (SOBI) thighs.
Similar types of raw chicken products were collected from supermarket chains and independent grocers or butcher shops in 33 large cities across Canada. Although a large proportion of retail chickens sold in supermarket chains are supplied by federally-registered establishments, approximately 20% of sampled chickens were purchased from independent grocers or butcher shops who may sell chicken products processed in provincially-inspected plants. The prevalence of Salmonella on whole carcasses and parts was significantly different with 21.0% (CI: 17.1% – 25.0%) and 31.6% (CI: 29.0% – 34.2%), respectively. However, the prevalence of Campylobacter on whole carcasses was 37.9% (CI: 33.1% – 42.6%), but not significantly different from parts with 43.1% (CI: 40.3% – 45.8%). When analyzed separately, the prevalence of both pathogens on SLBL breasts was not significantly different from SOBI thighs.
An important component of the MBS was to estimate bacterial counts on contaminated specimens. Enumerations were performed on all types of chicken meat products collected in abattoirs and food retail outlets. The geometric mean concentration of Salmonella was 0.11 and 0.09 MPN per ml of rinse fluid on abattoir and retail products, respectively. For Campylobacter, the geometric mean concentration was 3.81 and 1.83 CFU/mL on abattoir and retail products, respectively. It is worth noting that Salmonella counts were similar between different types of abattoir or retail products, in contrast to Campylobacter counts that were significantly lower on SLBL breasts whether they were collected in the abattoirs or food retail outlets.
Generic E. coli is used as a measure of fecal contamination in abattoirs. There were respectively 83.4% (CI: 81.1% – 85.7%), 83.9% (CI: 82.2% – 85.7%), and 95.0% (CI: 93.2% – 96.8%) of SLBL breasts, whole carcasses and SOBI thighs contaminated by generic E. coli. The geographic mean concentration was 51.4 CFU of generic E. coli per ml of rinse on abattoir products, reaching 96.1 CFU/mL for SOBI thighs.
In comparison with the 1997-98 poultry MBS, the prevalence of Salmonella on whole carcasses processed in federally-registered establishments significantly decreased from 21.1% (CI: 18.2% – 24.0%) to 16.9% (CI: 15.1% – 18.7%). No testing for Campylobacter was performed during the previous Canadian MBS preventing comparison with the current study.
This national MBS in broiler chicken provides current baseline estimates on the prevalence and concentration of Campylobacter and Salmonella at various stages along the broiler chicken meat supply chain. This information will be used as a science-based foundation by governments, industry and other stakeholders to inform the development of a risk management strategy for the control of Campylobacter and Salmonella in chicken produced in Canada. To achieve further reduction at processing or retail, a future strategy should consider the implementation of new interventions or mitigation measures along the supply chain from primary production to retail levels.
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