As part of a program to reduce numbers of the human pathogen Campylobacter on retail chickens twenty-two broiler processing lines, representing over 90% of United Kingdom (UK) production, were characterized by enumerating Campylobacter on pooled neck skins after the exsanguination, scalding, defeathering, evisceration, crop removal, inside-outside washing, and air-chilling stages of processing. Sixteen of the processing lines investigated showed significant (p<0.05) reductions in Campylobacter numbers because of carcass scalding. However, in all these lines, the following defeathering stage caused a significant increase in Campylobacter contamination that effectively negated the reductions caused by scalding. On four processing lines, primary chilling also caused a significant reduction in numbers of Campylobacter. On three lines, there was a significant microbiological benefit from inside-outside (I/O) washing. The stages where Campylobacter numbers were reduced require further investigations to determine the specific mechanisms responsible so that the observed pathogen reductions can be optimized, and more widely implemented. The transfer of up to 4 log cfu Campylobacter per gram of neck skin from a colonized flock to a following uncolonized flock was observed. The cross contamination was substantial and still detectable after 5,000 carcasses from an uncolonized flock had been processed. The numbers of Campylobacter recovered from the uncolonized flocks were highest on the first of the uncolonized birds to pass along the line and, in general, numbers fell as more uncolonized birds were processed. Air sampling recovered low numbers at the processing stages monitored, indicating that airborne transmission was unlikely to be the primary transfer mechanism operating for cross-contamination between flocks.
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