Enrichment and direct plating for detection of campylobacter in chicken liver rinse and exudate

Authors: Berrang, Mark; Cox Jr, Nelson; Thompson, Tori; Hinton Jr, Arthur; Yeh, Hung-Yueh

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2022
Publication Date: 6/20/2022
Citation: Berrang, M.E., Cox Jr, N.A., Thompson, T.M., Hinton Jr, A., Yeh, H. 2022. Enrichment and direct plating for detection of campylobacter in chicken liver rinse and exudate. Journal of Food Protection. https://doi.org/10.4315/jfp-22-131.
DOI: https://doi.org/10.4315/jfp-22-131

Interpretive Summary: Campylobacter is a leading cause of human food-borne illness; campylobacteriosis has been been epidemiologically linked to dishes prepared with undercooked chicken liver. It is important to know and use the best available methods when working to detect Campylobacter in chicken livers. We tested a variety of combinations of microbiological growth media (two enrichment broths and three solid plating media) for ability to detect naturally occurring Campylobacter in chicken livers that had been purchased at retail. We found that all tested combinations of media allowed detection of Campylobacter from chicken liver rinse and exudate to the same degree. Overall, exudate proved to be a more sensitive sample for detection of Campylobacter than did a liver rinse. All tested tubs of chicken liver purchased at retail (N=27) by at least one method tested. Campylobacter is prevalent in chicken livers and current methodology is adequate to detect the organism. Processors and researchers can use the methods described herein to determine the Campylobacter status of retail packages of chicken livers.

Technical Abstract: Because foodborne campylobacteriosis has been traced to undercooked chicken liver dishes, it is important to use the best available culture methods when testing for the presence of Campylobacter. We compared two Campylobacter enrichment broths (Bolton formulation and Neogen formulation) in combination with three selective plating media (Campy-Cefex, Campy-Line and RF Campylobacter agars) for detection of Campylobacter from fresh retail chicken livers. In each of three experiments, nine replicate tubs of chicken livers were sampled by drawing exudate and a pooled rinse of five whole liver lobes. Results are reported as number positive and compared by Fisher’s exact test. In Experiment 1, no combination of enrichment and plating media significantly outperformed another for detection of Campylobacter (P > 0.05); all tubs were found to include Campylobacter in both exudate and liver rinse. In Experiment 2, serial dilutions of samples were plated before and after enrichment. Exudate was found to be significantly more likely than rinse to support detection of Campylobacter by direct plating (P < 0.05); most exudate samples included at least 10 CFU Campylobacter pre mL Enrichment improved detection from rinse but not exudate; all enrichment and plating combinations resulted =1000 CFU per mL from most enriched samples. In Experiment 3, samples were diluted before enrichment to determine effect of enrichment on ever lower numbers of Campylobacter. Once again, enrichment did not improve recovery of Campylobacter from exudate (P > 0.05). However, enrichment of 10-2 diluted rinse improved detection (P < 0.05); at 10-3, the numbers of Campylobacter in rinse were too low to recover in most samples. Overall, all the media combinations tested were equivalent for detection of Campylobacter from chicken livers; liver exudate appears to be a more sensitive sample than rinse.