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The influence of transport, catching, and processing on contamination of broiler chickens with Salmonella and Campylobacter was investigated. Transport crates were reused with high frequency and were often still contaminated with Salmonella and Campylobacter when they arrived at the farm despite the fact that they were washed at the factory, and thus they were a potential route of infection. These organisms contaminated the feathers of previously Campylobacter-and Salmonella-negative birds going to the processing plant and were isolated from processed carcasses, albeit at a low frequency. The Campylobacter types which were the predominant organisms on the live birds when they arrived at the processing plant were not necessarily the types that were most frequently isolated from processed carcasses. This finding may reflect cross-contamination that occurred during processing or differences in the tolerance of the strains to the hostile environments that the bacteria experienced. The process of catching and putting the birds in crates significantly increased the chance of contamination with Campylobacter (P < 0.001).Human infections with Campylobacter spp. continue to be of international importance, and in England and Wales the number of confirmed cases continues to exceed 50,000 per annum (4). This is in line with the rate of Campylobacter infection in the United States, where the Centers for Disease Control and Prevention has estimated that the overall rate of infection is 1,000 cases per 100,000 people (28). Recent work on infectious intestinal disease in England and Wales (30) has indicated that cases are underreported and that the actual number of Campylobacter infections in these countries is likely to be about eight times the published number.Contaminated poultry meat is considered an important vehicle of human infection with Campylobacter (1,14,22,23), and because of the difficulties in controlling the spread of the bacteria in the kitchen (6, 7) and abattoir (17), control on the farm may be more effective. Identification of control measures requires a good understanding of the epidemiology of Campylobacter spp. in poultry meat production. There have been a number of studies of this important topic in recent years, and the environment (16), drinking water (28), and even vertical transmission (10, 24) have been suggested as possible sources of flock colonization. Improved farm hygiene measures, such as boot dipping (15) and boot changing (31), which presumably prevent the introduction of Campylobacter spp. from the external environment into a broiler chicken house, can either delay or prevent colonization. Transport vehicles and crates may be an additional source of contamination between batches of birds and farms (19). Such contamination may be particularly important for the introduction of Campylobacter into previously uninfected flocks during transport or during flock thinning (i.e., the removal of birds to reduce stock density) (12). Newell et al. (21) found that on one occasion carcasses from a Campylob...

Skirrow's medium is effective for isolating Campylobacters from human faeces but is less suitable for animal and environmental specimens owing to the presence of contaminating species. After determining the sensitivity of 104 strains of Campylobacters to several antimicrobial agents, used singly and in various combinations, a selective medium incorporating polymixin, rifampicin, trimethoprim and actidione, was developed. The medium, called Preston medium, was shown to be more selective than Skirrow's medium and suitable for any kind of specimen.

Fifteen kilometres of a river system traversing rural and urban areas and subject to sewage works effluent discharge was studied during a 12 1/2 month period. A total of 312 samples was collected from 12 sites at 14 d intervals and tested by a glass microfibre filtration method and a most probable number (MPN) method. Campylobacters were found in 43% of samples by the filtration method and 21% by the MPN method. The lowest frequency of isolation and lowest counts (less than 10 campylobacters/100 ml) were associated with samples collected from rural sites and fast-flowing stretches of river. The greatest frequency of isolation and highest counts (greater than 10-230 campylobacters/100 ml) were associated with sites adjacent to or downstream of sewage works. There was an obvious seasonal trend; most isolations and highest counts were obtained in late autumn and winter, and fewest isolations and lowest counts in spring and summer. Surface water run-off from adjacent farmland following heavy rainfall also increased the counts of campylobacters in the river system. Biotyping of isolates demonstrated that the most prevalent Campylobacter sp. was Campylobacter jejuni but C. coli, C. laridis and a previously unrecognized group of campylobacters were also isolated. Serotyping differentiated 14 serotypes of C. jejuni, 11 of C. coli and two of C. laridis. Furthermore, serotypes of C. jejuni commonly isolated from enteritis in man were frequently found in river water tested during this study.

SUMMARY The waterborne route of Vero cytotoxin‐producing E. coli (VTEC) O157 infection was first suggested in two unconnected human cases in 1985. Since then, waterborne VTEC O157 has been identified in sporadic cases and in outbreaks of illness. Recreational waters, private and municipal supplies have been implicated from microbiological, environmental and epidemiological studies of cases. In addition, a research cohort study of farm workers identified exposure to private water supplies as a risk factor for having antibodies to E. coli O157. Sources of contamination are thought to be animal and human faeces or sewage. The presence of low numbers of target organisms in water makes microbiological confirmation difficult, therefore epidemiological evidence has been essential in outbreak investigations. Despite the potential for contamination of water with VTEC O157, waterborne infection is relatively rare largely due to the susceptibility of the organism to water treatment processes. This paper presents the evidence for waterborne VTEC O157 infection, considering current microbiological, environmental and particularly epidemiological information.