Prevalence of Campylobacter in Dutch sewage purification plants

<p><em>Campylobacter</em> bacteria are an important cause of bacterial gastro-enteritis in man. Although food of animal origin is the main source of human infection, a casecontrol study in the United States of America showed that 8% of all campylobacteriosis cases could be attributed to consumption of contaminated surface water. In this thesis the prevalence of <em>Campylobacter</em> in sewage purification plants was investigated in order to obtain more information on the survival of this pathogen in aquatic environments. A survey carried out on three municipal plants showed that sewage and surface waters are frequently contaminated with <em>Campylobacter.</em> The contamination of sewage was higher when meat-processing industries were present in the drainage area of these plants. Indeed, drain water of a poultry abattoir contained high numbers of <em>Campylobacter</em> . It is clear that other sources contribute far lower numbers to sewage. Furthermore, the aquatic <em>Campylobacter</em> isolates were more resistant to quinolones and to ampicillin when a meat-processing industry was draining its waste on the sewerage.<p>The purification process reduced the numbers of <em>Campylobacter</em> , but this pathogen was not eliminated completely. The prevalence and reduction were not correlated with enviromnental parameters, such as water temperature and oxygen pressure.<p>The phenomenon of the transformation of spiral <em>Campylobacter</em> cells to coccoid cells was also investigated. Determination of several physiological parameters indicated that the contribution of the nonculturable, coccoid <em>Campylobacter</em> cells is to infection routes probably negligible.<p>Considering the observed occurrence of <em>Campylobacter</em> in surface waters, in the context of the reported dose-response model for this pathogen, it can be concluded that the role of surface waters in the epidemiology of <em>Campylobacter</em> may be underestimated