Sampling and testing conducted by Pennsylvania State University researchers demonstrated a low overall prevalence of Campylobacter on retail chicken meat; however, recovered C. jejuni strains did not match known poultry-associated genotypes, suggesting the need for sensitive detection methods and expanded genomic surveillance.

According to the study, Campylobacter has remained the leading bacterial cause of foodborne illness in the U.S. since 2014, with chicken—the most consumed meat in the U.S.—identified as the primary source of human infection. To better understand contamination levels, the researchers sampled and tested 209 skinless, boneless chicken breasts collected from seven grocery stores in State College, Pennsylvania, between October 2023 and July 2024. The meat samples were processed in at least eight states, as determined by packaging labels.

Using both culture-based enrichment and viability qualitative polymerase chain reaction (qPCR) methods, researchers found a low overall prevalence of Campylobacter, in just 1.9 percent of samples. Enrichments of 15 (7.2 percent) chicken breast samples produced visible colonies.

Whole genome sequencing (WGS) confirmed four isolates confirmed as Campylobacter jejuni. These isolates originated from chicken processed in Pennsylvania, Illinois, Virginia, and Delaware, and represented novel sequence types (STs), none of which were assigned to known clonal complexes.

Notably, direct plating and viability qPCR failed to detect Campylobacter in any sample, suggesting contamination levels were below the detection thresholds. Enrichment, which can detect as few as 12 cells per 325 grams (g), proved more sensitive than direct plating, with a threshold of 60 colony forming units (CFU)/325 g, and viability qPCR, at 3,200–5,000 cells/325 g. However, enrichment is susceptible to interference from competing microbes, requiring the incorporation of selective supplements to improve Campylobacter recovery.

The study also highlighted limitations in current surveillance. The recovered C. jejuni strains did not match common poultry-associated genotypes, indicating that existing databases may not fully reflect the diversity of Campylobacter in poultry environments. Additionally, antimicrobial resistance (AMR) genes associated with ampicillin and tetracycline were found in three isolates, though none showed resistance to fluoroquinolones or macrolides.

While the prevalence was low, the findings underscore the importance of sensitive detection methods and expanded genomic surveillance to better characterize Campylobacter contamination and inform risk assessments. Future research should compare enrichment media to optimize recovery from complex matrices like chicken rinses.

The study, published in the Journal of Food Protection, was conducted by researchers within the Pennsylvania Sate University Department of Food Science and One Health Microbiome Center. The work was supported in part by the U.S. Department of Agriculture’s National Institute of Food and Agriculture (USDA-NIFA) and USDA’s Hatch Appropriations.