ASSESSMENT OF THE DOSE-RESPONSE RELATIONSHIP OF CAMPYLOBACTER-JEJUNI

Mathematical relations describing the risk of infection after exposure to enteropathogens are important tools for the evaluation of the pote ntial health risk from exposure via food and water. A quantitative des cription of the dose-response relation for Campylobacter jejuni with t he Beta-Poisson model was fitted to experimental data of infection wit h Campylobacter jejuni (as determined by shedding of C. jejuni) obtain ed in human feeding studies performed by Black et al. (1988). The maxi mum likelihood estimates for the Beta-Poisson model parameters based o n these data are: <(alpha)over cap> = 0.145 and <(beta)over cap> 7.59. The fit of the model on the experimental data was good: the differenc e between the likelihood obtained with the Beta-Poisson model and the maximum possible likelihood was not significant. The occurrence of sym ptoms of intestinal illness did not follow a similar dose-related tren d. Overall, 22% of the infected volunteers developed symptoms (diarrhe a, fever). The highest illness-to-infection ratio was found at an inte rmediate dose (9 x 10(4)). The dose-response relation and the illness- to-infection ratio appeared to differ between different C. jejuni isol ates. The dose-response relation derived from feeding studies with a s ingle isolate should therefore be considered indicative. The absence o f experimental data in the low dose range resulted in a relatively lar ge confidence interval at low doses. However, in cases where the dose- response relation has been applied so far to estimate the health risk of exposure C. jejuni in water, the uncertainty in the dose-response r elation was insignificant compared to the uncertainty in the exposure estimate.