Study Links Bacteria in Processed Chickens to Contamination on Farm
The levels of bacteria in broiler chickens at the processing plant appears to be related to the amount of bacteria found among birds on the farm, according to a new study. Researchers at the University of Georgia, Athens looked at the prevalence and loads of Salmonella and Campylobacter in 55 flocks at a large chicken farm in Georgia and found that high levels of these bacteria on the farm corresponded to high levels on carcasses at the processing plant. Most cases of Campylobacter infection in the U.S. are associated with eating raw or undercooked poultry, according to the Centers for Disease Control and Prevention. A 2011 study conducted by the USDA’s Food Safety and Inspection Service found that of the Salmonella illnesses attributed to undercooked meat, poultry and eggs in the U.S., 48 percent are attributed to chicken, while 17 percent are attributed to turkey. In recent years, studies have found that between 50 and 80 percent of chickens sold at retail are contaminated with Campylobacter, while approximately 15 percent carry Salmonella. A 2010 Consumer Reports study found that, out of 382 chickens bought from more than 100 supermarkets, food stores, and mass merchandisers in 22 states, 62 percent contained Campylobacter, 14 percent contained Salmonella and 9 percent contained both. While previous studies have linked the presence of Campylobacter and Salmonella on the farm to their presence in chickens at processing, this study was the first to examine the relationship between pathogen loads (the amount of the pathogens found) at the farm and at the processing plant. The study reported “a direct linear relationship between the mean Salmonella load…of farm samples and the mean Salmonella load of carcass rinses.” For Campylobacter, loads on the farm were still predictors of loads at processing, but the amount tended to increase exponentionally from farm to processing. “The Campylobacter loads of all four farm sample types were significantly associated with Campylobacter loads of post-chill carcass rinses,” noted the report. Salmonella was detected in farm samples from 96 percent of flocks that also had Salmonella at the processing stage, while Campylobacter was identified among 71 percent of flocks among which the bacteria was also detected during processing. This association between farm and processing plant contamination points to a need to focus on methods to prevent contamination on the farm, according to the researchers. “This study suggests that reducing foodborne pathogen loads on broiler chicken farms would help to reduce pathogen loads at processing, and may ultimately help to reduce the risk of foodborne illness,” said Roy Berghaus, an author on the study in a press release. “This is important because most of our efforts towards reducing foodborne pathogens are currently focused on what happens during processing. Processing interventions are effective but they can only do so much.” For Salmonella prevention, these on-farm practices may include vaccination of breeder hens, treatment of newly hatched chicks with a competitive exclusion product, which prevents colonization of pathogenic bacteria in the gut of the bird, and the use of acidified water during feed withdrawal. However, the researchers point out, no known methods have been effective at reducing Campylobacter among flocks. Thus efforts to prevent the pathogen from entering the birds’ environment through strict biosecurity measures would be the only recourse for combatting Campylobacter on the farm. Post-processing freezing has also been shown to reduce Campylobacter loads, note the authors. The study was published ahead of print in Applied and Environmental Microbiology.