Campylobacter spp. contamination of chicken carcasses during processing in relation to flock colonisation

V. M. Allen, S. A. Bull*, J. E.L. Corry, G. Domingue, Frieda Jorgensen, J. A. Frost, R. Whyte, A. Gonzalez, Nicola Elviss, T. J. Humphrey

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    133 Citations (Scopus)


    The presence and numbers of campylobacters on chicken carcasses from 26 slaughter groups, originating from 22 single-house flocks and processed in four UK plants, were studied in relation to the level of flock colonisation determined by examining the caecal contents of at least ten birds per group. The prevalence of campylobacters on carcasses from five campylobacter-negative flocks processed just after other negative flocks was low (≤ 30%). Campylobacters were isolated from 90 to 100% of carcasses from three flocks which were partly colonised, with 5, 5 and 30% of caecal contents positive, and which were processed after fully colonised flocks. All carcasses from the remaining fully colonised flocks were contaminated with campylobacters, and they had significantly (P < 0.001) higher numbers per carcass (average of 5.3 log10 cfu; range: 1.3 to > 8.0 log10 cfu) than carcasses originating from low prevalence flocks (average of 2.3 log10 cfu; range: < 1.1 to 4.1 log10 cfu). There was a reduction in the numbers of campylobacters on carcasses between plucking and chilling in eight of ten fully colonised flocks. In another eight flocks, a significant (P < 0.001) decrease (0.8 log10 cfu) in the number of campylobacters on carcasses from just before to after chilling was detected. Campylobacter spp. could be isolated from aerosols, particles and droplets in considerable numbers in the hanging-on, defeathering and evisceration areas but not in the chillers. This was the case even when campylobacters were not isolated from the target flock. Campylobacters on carcasses from two partly colonised flocks were either the same subtype, as determined by speciation, Multi-Locus Sequence Typing (MLST) and flaA Restricted Fragment Length Polymorphism (RFLP) typing, as those in the fully colonised flocks processed previously, although not necessarily the most prevalent ones; or were the same subtypes as those found in the caeca of the flock itself. The prevalences of the different campylobacter subtypes found on carcasses from two fully colonised flocks did not closely reflect those found in the caeca. MLST combined with flaA RFLP provided a good method for ascertaining the relatedness of strains isolated from carcasses and caecal contents. This study showed that carcass contamination is related to the within-flock prevalence of campylobacter colonisation, but that contamination from previously processed flocks was also significant, especially on carcasses from low prevalence flocks. Forced dry air cooling of carcasses reduced contamination levels.

    Original languageEnglish
    Pages (from-to)54-61
    Number of pages8
    JournalInternational Journal of Food Microbiology
    Issue number1
    Publication statusPublished - 1 Jan 2007

    Bibliographical note

    Funding Information:
    The authors would like to thank the staff at the poultry processing companies for their kind co-operation. We would also like to thank Karen Mattick, Ann Del-Sol, Marco Siccardi, Karen Martin and Jill Harris for their technical assistance and Toby Knowles for his excellent statistical advice. Assistance with sero/phage typing of campylobacters was gratefully received from Helen Wicken and Richard Thwaites. We are also extremely grateful for the MLST typing data performed by Professor Maiden′s team of Frances Colles and Alison Cody at the University of Oxford, UK. The work was supported by the UK Food Standards Agency (project code BO3008).


    • Caecal contents
    • Campylobacter subtypes
    • Carcass contamination
    • Poultry processing


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