Through-chain Enumeration and Genotyping of Campylobacter spp. in Broiler Chicken Production

Introduction: Campylobacter jejuni and C. coli are the leading causes of human foodborne bacterial gastroenteritis worldwide and frequently colonize poultry. These organisms become highly prevalent in broiler flocks after 2-3 weeks of age (∼ 65% prevalence and 6-8 log CFU/g feces) and are widely disseminated during processing (∼85% post-chill positive, mean 0.70 log CFU/cm²). However, there are few studies which have attempted to quantify Campylobacter spp. in the same flock from primary production to processing, as well as tracking the genetic diversity of isolates.

Purpose: To determine (i) the time and levels of Campylobacter colonization in broiler chickens, (ii) the effect of commercial processing steps on the reduction of Campylobacter spp., and (iii) the sources and genetic diversity of the organism using rep-PCR fingerprinting.

Methods: Using a semi-quantitative technique, levels of Campylobacter were determined in broiler flocks from placement to processing. Feces (n = 350) and environmental samples from four free-range and conventional farms in the Sydney basin were analyzed at weekly intervals. Various samples (n = 180) from three of the flocks were collected throughout processing, from delivery to post-chill, and analyzed. Confirmed C. jejuni and C. coli isolates (n = 270) were selected and typed using rep-PCR for cluster analysis and classified against a library containing strains previously characterized using flaA-RFLP and MLST.

Results: Colonization of the broilers occurred as early as 7 days, with 100% infection of the flock between 2-3 weeks of age (mean 6 log CFU/g faeces). A significant 5 log reduction in Campylobacter levels was observed post-spin chill. There was broad genetic diversity among Campylobacter species, with seven clusters of C. jejuni and five clusters of C. coli.

Significance: Determination of the sources and time of colonization, in addition to baseline data, allows for the development of targeted intervention strategies for the control of Campylobacter spp. in broiler chickens.