Salmonella bacteria is one of the most common causes of food poisoning, with poultry contributing to more than one-fifth of salmonella infections. According to the U.S. Department of Agriculture-Food Safety Inspection Service (USDA-FSIS), the incidence of Salmonella in poultry during processing decreased from 9% to 6.57% between 2016 and 2020, but the incidence of human salmonella cases has remained stable during the same period. Researchers from the University of Georgia have investigated the different types of Salmonella found in poultry that can cause human illness, and have used a high-resolution technique to unveil strains in living birds that can not be detected by traditional methods.
The University of Georgia researchers worked with the Georgia Poultry Lab Network in Gainesville, Georgia to investigate the Salmonella serotypes found in both live breeder chickens and postharvest chicken products. The team found an apparent discrepancy between serotypes found in the live chickens compared to samples at processing plants. In birds at a Georgia farm, the most abundant and easily detectable strain was the Kentucky serotype, which accounted for 80% of all Salmonella found on the farm. However, this serotype was less abundant in processed chicken, suggesting it can be effectively removed during processing. The Kentucky serotype is not commonly associated with human illness, but three other types – Infantis, Enteritidis and Schwarzengrund – were also found in samples at processing plants. Despite being detected in postharvest poultry, these strains could not be detected in live birds at the farm using traditional culture methods.
The team turned to a newer technique developed at the University of Georgia in 2015 which could allow these less abundant, more harmful strains of Salmonella to be detected on the farm. Known as CRISPR-SeroSeq, the technology identifies molecular signatures in the bacteria’s CRISPR regions, providing higher resolution than traditional techniques. Using CRISPR-SeroSeq, the researchers were able to detect the additional strains in live birds that had not been detected before despite being present in postharvest samples. The ability to identify more strains on the farm can inform Salmonella control strategies such as vaccinations of birds by poultry veterinarians. This research was published in Food Microbiology.
“Our main focus is to make sure that at the end of the day we’re facilitating improvements in the poultry industry,” said first author Amy Siceloff. “Now that we’re aware of this gradual increase in serotypes and that they don’t just pop up overnight, this kind of surveillance is going to be key in managing salmonella moving forward.”
Photo: Chickens roam a backyard in Athens, Georgia. Credit: Chad Osborn, University of Georgia