Ruminant livestock, particularly cattle, is considered the primary reservoir of Escherichia coli O157:H7. This study examines the transmission of E. coli O157:H7 within groups of cattle during winter housing. Holstein Friesian steers were grouped in six pens of five animals. An animal inoculated with and proven to be shedding a marked strain of E. coli O157: H7 was introduced into each pen. Fecal (rectal swabs) and hide samples (900 cm2 from the right rump) were taken from the 36 animals throughout the study. Water, feed, and gate or partition samples from each pen were also examined. Within 24 h of introducing the inoculated animals into the pens, samples collected from the drinking water, pen barriers, and animal hides were positive for the pathogen. Within 48 h, the hides of 20 (66%) of 30 cohort animals from the six pens were contaminated with E. coli O157:H7. The first positive fecal samples from the noninoculated cohort animals were detected 3 days after the introduction of the inoculated steers. During the 23 days of the study, 15 of 30 cohort animals shed the marked E. coli O157:H7 strain in their feces on at least one occasion. Animal behavior in the pens was monitored during a 12-h period using closed circuit television cameras. The camera footage showed an average of 13 instances of animal grooming in each pen per hour. The study suggests that transmission of E. coli O157:H7 between animals may occur following ingestion of the pathogen at low levels and that animal hide may be an important source of transmission.

Escherichia coli O157:H7 is an important foodborne pathogen that can cause hemorrhagic colitis and hemolytic uremic syndrome. Cattle feces and fecally contaminated water are important in the transmission of this organism on the farm. In this study, the survival of E. coli O157:H7 in feces and water was compared following passage through the animal digestive tract or preparation in the laboratory. Feces were collected from steers before and after oral inoculation with a marked strain of E. coli O157:H7. Fecal samples collected before cattle inoculation were subsequently inoculated with the marked strain of E. coli O157:H7 prepared in the laboratory. Subsamples were taken from both animal and laboratory-inoculated feces to inoculate 5-liter volumes of water. E. coli O157:H7 in feces survived up to 97 days, and survival was not affected by the method used to prepare the inoculating strain. E. coli O157:H7 survived up to 109 days in water, and the bacteria collected from inoculated cattle were detected up to 10 weeks longer than the laboratory-prepared culture. This study suggests that pathogen survival in low-nutrient conditions may be enhanced by passage through the gastrointestinal tract.

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Aims:The study aimed to investigate the survival characteristics of Escherichia coli O157:H7 in farm water (FW), and in sterile distilled municipal water (SDW), stored outdoors under field conditions, with or without the addition of faeces (1% w ⁄ v), in a farmyard shed and the laboratory at 15°C. Methods and Results: Water samples were inoculated with E. coli O157:H7 at 10 3 and 10 6 ml )1 , and sampled over a 31-day period. In FW stored outdoors in a field, E. coli O157:H7 survived for 14 days at temperatures <15°C, at both inoculation levels, while in the laboratory at 15°C, the organism was still detectable at low levels (<1 log 10 cfu ml )1 ) after 31 days. The addition of bovine faeces to water outdoors (1% w ⁄ v) resulted in survival for 24 days. In SDW inoculated at 10 6 ml )1 and stored in the laboratory (15°C), only a 2AE5 log reduction was observed after 31 days, while the organism could not be detected after 17 days in the field. Preliminary screening of water samples stored outdoors isolated a bacterium which exhibited antimicrobial activity towards E. coli O157:H7. Conclusions: The survival of E. coli O157:H7 observed in this study illustrates the potential of farm water to act as a vehicle in the transfer of the organism across a herd. Significance and Impact of the Study: The difficulty in extrapolating results from controlled laboratory situations to on-farm conditions is also highlighted in this study.

Aims: The survival characteristics of Escherichia Coli O157:H7 were investigated in bovine slurry from cattle fed two different diets: (i) silage and (ii) silage + concentrates. Methods and Results: Slurry samples collected from freshly-agitated tanks were inoculated at a level of log 10 6á0 cfu g)1 and stored in the laboratory at 10°C. Over a 12 week storage period, a 3á5 and 5á5 log reduction was observed in slurry from cattle fed a silage and silage plus concentrate diet, respectively. Conclusions: The persistence of E. coli O157:H7 in slurry over a 3 month storage period indicates its potential for transmitting the organism back into the environment. Singi®cance and Impact of the Study: The discussion concludes however, that despite pathogen survival in slurry, it may not represent a major source of transmission in the farm environment.