A comparison of risk assessments on Campylobacter in broiler meat.

In recent years, several quantitative risk assessments for Campylobacter in broiler meat have been developed to support risk managers in controlling this pathogen. The models encompass some or all of the consecutive stages in the broiler meat production chain: primary production, industrial processing, consumer food preparation, and the dose-response relationship. The modelling approaches vary between the models, and this has supported the progress of risk assessment as a research discipline. The risk assessments are not only used to assess the human incidence of campylobacteriosis due to contaminated broiler meat, but more importantly for analyses of the effects of control measures at different stages in the broiler meat production chain. This review paper provides a comparative overview of models developed in the United Kingdom, Denmark, the Netherlands and Germany, and aims to identify differences and similarities of these existing models. Risk assessments developed for FAO/WHO and in New Zealand are also briefly discussed. Although the dynamics of the existing models may differ substantially, there are some similar conclusions shared between all models. The continuous introduction of Campylobacter in flocks implies that monitoring for Campylobacter at the farm up to one week before slaughter may result in flocks that are falsely tested negative: once Campylobacter is established at the farm, the within-flock prevalence increases dramatically within a week. Consequently, at the point of slaughter, the prevalence is most likely to be either very low (<5%) or very high (>95%). In evaluating control strategies, all models find a negligible effect of logistic slaughter, the separate processing of positive and negative flocks. Also, all risk assessments conclude that the most effective intervention measures aim at reducing the Campylobacter concentration, rather than reducing the prevalence. During the stage where the consumer handles the food, cross-contamination is generally considered to be more relevant than undercooking. An important finding, shared by all, is that the tails of the distributions describing the variability in Campylobacter concentrations between meat products and meals determine the risks, not the mean values of those distributions. Although a unified model for risk assessment of Campylobacter in the broiler meat production would be desirable in order to promote a European harmonized approach, it is neither feasible nor desirable to merge the different models into one generic risk assessment model. The purpose of such a generic model has yet to be defined at a European level and the large variety in practices between countries, especially related to consumer food preparation and consumption, complicates a unified approach.

Detection of seven virulence and toxin genes of Campylobacter jejuni isolates from Danish turkeys by PCR and cytolethal distending toxin production of the isolates.

A total of 117 Campylobacter jejuni isolates from Danish turkeys were tested for the presence of seven virulence and toxin genes by PCR. One hundred seventeen (100%) isolates were positive for flaA, cadF, and ceuE gene primers. One hundred three (88%) isolates were positive for cdt gene cluster PCR detection (cdt gene cluster-PCR), whereas 101 (86.3%), 102 (87.2%), and 110 (94%) isolates were positive for cdtA-, cdtB-, and cdtC-PCR, respectively. Only 39 (33.3%) isolates were positive for virB11. Of 117 isolates, 114 (97.4%) produced cytolethal distending toxin (CDT) in Vero cell assays, 105 (89.7%) in Colon 205 assays, and 109 (93.2%) in chicken embryo cell assays. The CDT titers were determined in Vero cell assays. Of 117 isolates, 50 (42.7%) produced a CDT titer of 1:100, 29 (24.8%) of 1:50, and 27 (23%) of 1:5 to 1:10; 8 (6.8%) produced a CDT titer at undiluted supernatants and 3 (2.6%) produced no toxin. Twenty-nine C. jejuni isolates that were PCR negative for one or more individual cdt toxin genes also produced low or no CDT toxin. The high prevalence of the seven virulence and toxin genes demonstrates that these putative pathogenic determinants are widespread among Campylobacter isolates from turkeys and calls for further investigation for the elimination of Campylobacter infection in industrial turkey production and in industrial food chains.