Detection of Campylobacter spp. and Yersina spp. in chicken burgers: Critical evaluation of CIN medium and characterization of psychrotolerant microbiota in commercial samples from Reus (Tarragona, Spain).

Two of the three most prevalent bacterial genera associated with human diseases caused by meat consumption are Campylobacter (mainly in poultry meat) and Yersinia (in pork meat). As its detection and quantification is not regulated by the European legislation (except for the quantification of Campylobacter in poultry channels), several samples of chicken burgers from different establishments including supermarkets and retail trade outlets in Reus (Spain) were processed to ensure microbiological safety. Microbiological criteria and procedures have been those included in the European standards for Campylobacter (Regulation No. 2017/1495) and Yersinia (ISO 10273:2917). Results showed the absence of Campylobacter spp. in all samples, but high counts (10⁴ to 5×10⁵CFU/g) of typical colonies ("red bull's eye" morphology) on CIN medium compatible with Yersinia spp. The biochemical profile of the strains from the typical colonies, and their subsequent molecular identification using MALDI-TOF MS enabled us to identify Yersinia intermedia in just one sample, and Pseudomonas and Serratia liquefaciens in the remaining ones. These findings call into question the usefulness of CIN medium for detecting Yersinia spp. in food. Moreover, the presence of high counts of psychrotolerant bacteria from the genera Pseudomonas and Serratia highlight the need to improve hygienic conditions in the procedures used to produce meat derivatives.