Fate of Enterohemorrhagic Escherichia coli O157:H7 in Bovine Feces
Applied and Environmental Microbiology , 62 , 1996
Wang, G., Zhao, T., Doyle, M.P.
Dairy cattle have been identified as a principal reservoir of Escherichia coli O157:H7. The fate of this pathogen in bovine feces at 5, 22, and 37&C was determined. Two levels of inocula (103 and 105 CFU/g) of a mixture of five nalidixic acid-resistant E. coli O157:H7 strains were used. E. coli O157:H7 survived at 37&C for 42 and 49 days with low and high inocula, respectively, and at 22&C for 49 and 56 days with low and high inocula, respectively. Fecal samples at both temperatures had low moisture contents (about 10%) and water activities (<0.5) near the end of the study. E. coli O157:H7 at 5&C survived for 63 to 70 days, with the moisture content (74%) of feces remaining high through the study. Chromosomal DNA fingerprinting of E. coli O157:H7 isolates surviving near the completion of the study revealed that the human isolate strain 932 was the only surviving strain at 22 or 37&C. All five strains were isolated near the end of incubation from feces held at 5&C. Isolates at each temperature were still capable of producing both verotoxin 1 and verotoxin 2. Results indicate that E. coli O157:H7 can survive in feces for a long period of time and retain its ability to produce verotoxins. Hence, bovine feces are a potential vehicle for transmitting E. coli O157:H7 to cattle, food, and the environment. Appropriate handling of bovine feces is important to control the spread of this pathogen.