Water-borne outbreak of campylobacter gastroenteritis.

An outbreak of gastroenteritis affecting 234 pupils and 23 staff at a boarding school occurred over a period of 8 weeks. Campylobacter spp. were isolated from pupils and staff, and from two samples of cold water taken from an open-topped storage tank which supplied predominantly unchlorinated water to the main school building. The two isolates from water were of the same serotype. This serotype was the commonest of the three serotypes of Campylobacter jejuni detected in isolates from pupils and staff. There was a highly significant association between consumption of water from the cold water storage tank and reported illness in staff. Attack rates in pupils corresponded closely with the extent of distribution of this water-supply to the main residential houses. Contamination of water by faecal material from birds or bats was the most likely source of infection.

An experimental study of the pathology and ecology of Yersinia enterocolitica infection in mice.

Four experiments are described in which laboratory mice were infected with Y. enterocolitica using an American serotype 0:8 (WA) and two European strains, serotypes 0:3 and 0:9. The pathogenicity and histopathological responses of strain WA (0:8) were determined in the Porton white outbred mouse by three route of inoculation. The LD50 after infection by the intraperitoneal route was 8.8 x 10(1) organisms, which is similar to results obtained by previous workers using disease-free and hybrid mouse strains. European strains 0:3 and 0:9 were shown to infect the Porton white outbred mice when injected intraperitoneally but no deaths occurred. Chronic faecal excretion was demonstrated up to 135 days. Specific antibodies were detected in the 0:3 and 0:9 infected mice and the immune response was further assessed by challenging the excreter mice with 50LD50S of the virulent WA strain. A significant degree of protection occurred in mice previously injected with 10(7) organisms of the avirulent strains. No evidence of phenotypic variation, as measured by 40 markers, was detected in 67 isolates of Y. enterocolitica recovered during the course of the four experiments. These results suggest that laboratory rodents could be a useful model for studying the infection produced by virulent and avirulent strains, and since it has been clearly established that a wide range of serotypes and non-typeable strains may be isolated from wild rodents, our findings could be extrapolated to the wildlife situation. Further work on the laboratory model could give a more detailed insight into the mechanism and extent to which rodents act as reservoirs of Y. enterocolitica.

A microagglutination test for Yersinia enterocolitica infection: recognition of multiple serotypes in experiments with stained suspensions of serotype O5,27.

When suspensions of Yersinia enterocolitica were stained with triphenyl-tetrazolium chloride (TTC) their antigenic specificity, as determined by tube and microtitre-plate agglutination tests, was altered. Thus, a TTC-stained suspension of serotype O5,27 detected antibodies to nine O serotypes of Y. enterocolitica in sera from experimentally infected animals but did not cross-react with antisera to organisms of five other unrelated genera including Brucella. The same suspension did, however, cross-react weakly with antisera to four serotypes of Yersinia pseudotuberculosis. The value of this antigen preparation in detecting antibodies to the wide range of Y. enterocolitica serotypes likely to cause infection in man should now be assessed.

Long-term fecal excretion and resistance induced in mice infected with Yersinia enterocolitica.

European isolates of Yersinia enterocolitica serotypes O3 and O9 were shown to infect but not kill mice, which became fecal excreters for up to 135 days. The mice challenged with 500 50% lethal doses of the virulent WA strain of Y. enterocolitica serotype O8 survived, and some excreted the virulent strain. This rodent model may be of value in assessing the ecological significance of rodents in the maintenance of Y. enterocolitica.