Validation of a Campylobacter Real-time PCR Assay for the Detection of Campylobacter in Chicken Carcass Rinses, Turkey Carcass Sponges and Raw Ground Chicken after a 24 h Enrichment

Introduction: Campylobacter has emerged as the most frequent cause of gastroenteritis in humans. C. jejuni, C. coli, and C. lari are the species most commonly identified as causing infection.  The majority of Campylobacter infections are acquired through the consumption of contaminated water, raw and inadequately pasteurized milk, and undercooked meats, particularly poultry.  Surveillance through FoodNet indicates that over 2.4 million people are infected by Campylobacter each year.

Purpose: iQ-Check Campylobacter is a real-time PCR assay for detection of C. jejuni, C. coli, and C. lari in chicken carcass rinses, turkey carcass sponges and raw ground chicken.  The data presented is the AOAC Performance Tested Method validation study for this assay.

Methods: Inclusivity and exclusivity tests were performed to determine sensitivity and specificity of the assay.  The proposed method was compared to the USDA MLG reference method for the analysis of chicken carcass rinses and turkey sponges and to the ISO reference method for the analysis of raw ground chicken.  Chicken rinses and turkey sponges were naturally contaminated and two lots of each matrix were tested.  Raw ground chicken was inoculated at two levels: a low level at 0.619 CFU/25g and a high level at 6.19 CFU/25g.

Results: Inclusivity and exclusivity testing yielded 100% accuracy.  When food matrices were tested, all samples that were detected by the new method were subsequently confirmed by reference method protocol.  There was no significant difference in the number of positive samples detected by the proposed Campylobacter kit in comparison to the USDA or ISO method for all matrices tested. 

Significance: The new Campylobacter kit can be used after a single 24-hr primary enrichment.  The culture method requires a 48-hr enrichment followed by another 48 hrs on a selective agar plate.  The iQ-Check kit uses primers and specific DNA hybridization probes targeting a specific sequence on the Campylobacter genome.  Detecting target DNA is possible even if the cells are stressed or in lower numbers.  This increased sensitivity and time saving provide users with an alternative to the reference method for detection of Campylobacter in food samples to meet current regulatory demands.