Escherichia coli O157 infections are the cause of sporadic or epidemic cases of often bloody diarrhea that can progress to hemolytic uremic syndrome (HUS), a systematic microvascular syndrome with predominately renal and neurological complications. HUS is responsible for most deaths associated with E. coli O157 infection. From March 2002 to February 2004, approximately 13,000 fecal pat samples from 481 farms with finishing/ store cattle throughout Scotland were examined for the presence of E. coli O157. A total of 441 fecal pats from 91 farms tested positive for E. coli O157. From the positive samples, a point estimate for high-level shedders was identified using mixture distribution analysis on counts of E. coli O157. Models were developed based on the confidence interval surrounding this point estimate (high-level shedder, greater than 10 3 or greater than 10 4 CFU g ؊1 feces). The mean prevalence on high-level-shedding farms was higher than that on low-levelshedding farms. The presence of a high-level shedder on a farm was found to be associated with a high proportion of low-level shedding, consistent with the possibility of a higher level of transmission. Analysis of risk factors associated with the presence of a high-level shedder on a farm suggested the importance of the pathogen and individual host rather than the farm environment. The proportion of high-level shedders of phage 21/28 was higher than expected by chance. Management-related risk factors that were identified included the type of cattle (female breeding cattle) and cattle stress (movement and weaning), as opposed to environmental factors, such as water supply and feed.Verocytotoxin-producing Escherichia coli (VTEC), such as E. coli O157, is an important zoonotic agent with worldwide distribution. E. coli O157 may cause sporadic or epidemic cases of often bloody diarrhea that can progress to hemorrhagic colitis, thrombotic thrombocytopenic purpura, and hemolytic uremic syndrome (HUS) (21). HUS is a systematic microvascular syndrome that is initiated by secreted shiga toxins, with predominately renal and neurological complications, which are responsible for most deaths associated with E. coli O157 infection, particularly among elderly patients (22). Infection with E. coli O157 is a leading cause of acute renal failure in children (8). The incidence of E. coli O157 infection in Scotland is substantially higher than elsewhere in Great Britain (28) Healthy cattle shed E. coli O157 in their feces (9,17,35), and this pathogen is present in most cattle operations (48). Cattle are the main reservoir host for E. coli O157 and other VTEC in the developed world (1) and play a significant role in the epidemiology of human infections (13). Outbreaks are attributed to consumption of contaminated food and water, animal contact, and person-to-person transmission (51). However, case control studies of sporadic infections, which account for the majority of cases of E. coli O157 infection in Scotland, have indicated direct contact with animals, their feces, and/...

Listeria monocytogenes was isolated in low numbers from a variety of environmental samples associated with the primary production of food, including vegetation, faeces and meat. The organism was rarely detected on growing grass and vegetables prior to processing. The excretion of L. monocytogenes by farm animals was linked to their diet, with animals fed entirely on hay or manufactured diets not excreting detectable levels of Listeria (i.e. absence in 25 g). However, animals fed on silage, which is frequently contaminated with L. monocytogenes, commonly excreted the organism. Transport of live animals over long distances (> 100 km) significantly increased the level of excretion of Listeria, but the contamination of carcasses of sheep and cattle was not high. Pigs and poultry faeces were free of Listeria prior to slaughter and pig carcasses were not found to have Listeria present. Frozen and chilled chicken did show detectable levels reflecting the greater potential for contamination during poultry processing. Samples of minced beef were tested and 21 of 23 samples were positive for L. monocytogenes, demonstrating that processing significantly increases the level of contamination compared to whole carcasses. Multilocus enzyme electrophoresis of a representative selection of the isolates showed that there was a wide range of electrophoretic types present in the primary production environment, relatively few of which have been linked to cases of human listeriosis. However, these types do arise on farms and occasional contamination of food raw material by potentially virulent strains may be sufficient to allow adaptable strains to become established in the processing environment and thus be responsible for more widespread contamination of the food available to the consumer.

A method for the isolation of listeria which enabled a more rapid detection of the organism was used to examine samples of silage and bird faeces. Faecal samples indicated that seagulls feeding at sewage works had a higher rate of carriage than those elsewhere. Faecal samples from rooks generally suggested a low incidence of listeria except on one occasion when eight of twenty samples contained Listeria monocytogenes: this coincided with the nesting season and the peak period for listeriosis in sheep. The incidence of L. monocytogenes in clamp silages ranged from 2.5-5.9%, but in samples of big bale silages the incidence was 22.2% and, when mouldy samples were selected, 44%.

SUMMARY The fate of both faecal Escherichia coli and E. coli O157 in slurry following application to arable and grass plots on a clay loam soil was studied. Slurry (5% dry matter) containing 53 × 104 ml−1 E. coli and 30 E. coli O157 100 ml−1 was spread in early March. Initially, almost all E. coli were retained in the upper layers of the soil. Escherichia coli numbers steadily declined to less than 1% of those applied by day 29, and E. coli O157 were only detected in the soil and on the grass for the first week after application. There was some transport of bacteria to deeper layers of the soil, but this was approximately 2% of the total; transport to drains over the same period was mainly associated with rainfall events and amounted to approximately 7% of applied E. coli. However, there were indications that periods of heavy rainfall could cause significant losses of E. coli by both leaching and run‐off. Experimental studies showed that E. coli O157 on grass, which was subsequently ensiled in conditions allowing aerobic spoilage, could multiply to numbers exceeding 106 g−1 in the silage.

Aim: To determine the rate of antibiotic resistance transmission between commensal and pathogenic representatives of the Enterobacteriaceae. Methods and Results: Through the use of a validated in vitro simulation of the porcine ileum, the transmission of antibiotic resistance was detected between commensal Escherichia coli, E. coli O157 and Salmonella spp. Countable transconjugant populations arose readily and, in one example, proved capable of indefinite persistence. Conclusions: Genetic material conferring antibiotic resistance is readily transmissible between members of the Enterobacteriaceae under ileal conditions. Recipient phenotype influences the persistence of multi-resistant transconjugants. Significance and Impact of the Study: The observation that the conjugal transmission of antibiotic resistance is commonplace under ileal conditions impacts primarily on the risk of food contamination by multi-resistant bacteria. The establishment of a multi-resistant transconjugant population as a dominant member of the microflora maintains a genetic reservoir of antimicrobial resistance.