Longitudinal Emergence and Distribution of Escherichia coli O157 Genotypes in a Beef Feedlot

Abstract

The purpose of this study was to describe the prevalence and longitudinal distribution of Escherichia coli O157 in feedlot cattle and the feedlot environment. Pen floors, water tanks, other cattle in the feedlot, feed, and bird feces were sampled for 2 weeks prior to entry of the study cattle. Twelve pens of study cattle were sampled twice weekly. At each sample time cattle feces, water from tanks in each pen, bunk feed, feed components, bird feces, and houseflies were collected. Bunk feed samples were collected before and after cattle had access to the feed. Overall, 28% of cattle fecal samples, 3.9% of bird fecal samples, 25% of water samples, 3.4% of housefly samples, 1.25% of bunk feed before calf access, and 3.25% of bunk feed samples after cattle had access to the feed were positive for E. coli O157. Genetic analysis of E. coli O157 isolates was done using pulsed-field gel electrophoresis (PFGE). PFGE types identified in sampling of the feedlot prior to calf entry were different than the majority of types identified following calf entry. A single strain type predominated in the samples collected after entry of the cattle. It was first identified 5 days after entry of the first pen of cattle and was subsequently identified in all pens. Data support that the incoming cattle introduced a new strain that became the predominant strain in the feedlot.Escherichia coli O157 is an important cause of hemorrhagic colitis and hemolytic uremic syndrome in humans (3, 7) and has been particularly associated with the consumption of ground beef. Research on Escherichia coli O157 has identified important aspects of preharvest ecology but has failed to identify validated critical control points for E. coli O157 in the feedlot. Individual cattle can be transiently colonized with E. coli O157 for 30 to 60 days (5, 12, 15, 16), but no persistent colonization has been shown. Prevalence in cattle has a seasonal distribution, being low in winter and higher in summer (12,15,16,29). Further, individual genotypes of O157 have been shown to persist on individual farms over time despite population turnover (19,22,25). The source of the bacteria that colonize cattle is unknown, but feed and water are commonly contaminated with coliforms (26), suggesting fecal contamination. E. coli O157 can survive for an extended period in bovine feces (13,17) and may serve as a source of contamination for feed or water. E. coli O157 is commonly found in water tanks and can persist for an extended period there (20), and it has also been commonly found in cattle feeds (9). Additionally, E. coli O157 has been identified in a wide range of other animals, including flies, birds, dogs, horses, and opossum (2,6,24,30,32), potentially providing opportunity for cattle exposure.The complex nature of E. coli O157 ecology in feedlots suggests that a reservoir other than cattle may be important in maintenance of E. coli O157. The feedlot environment, feed, water, or other animals may be an important source of outside exposure. The role of the environment in the ma...

Effect of backgrounding and transition diets on fecal concentration and strain types of commensalEscherichia coliin beef cattle

“…These results suggest that either the higher concentrate amounts in the transition phase or the length the cattle are the same cohort (109 d) could aid the persistence of closely related strain types shed. Sanderson et al (2006) made similar observations for pathogenic E. coli and reported change in the strain types over time, but at a much faster rate than observed in this study. In that study, it was reported that PFGE types prior to entry into the feedlot were different from the majority of types identified after entry whereby a single strain type, which was first identified 5 d after entry of cattle, predominated among animals and was subsequently identified in all pens.…”

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Prevalence and Impact of Bacteriophages on the Presence of Escherichia coli O157:H7 in Feedlot Cattle and Their Environment

“…This study used a random subset of rectal fecal samples collected from a much larger investigation of E. coli O157:H7 in feedlots A and B (T. P. Stephens, unpublished data). In this study, the overall prevalence of E. coli O157:H7 in fecal grab samples (23.9%) was high but not unlike that reported previously (20). The high numbers of host persisting during the study period likely increased phage prevalence.…”

Effect of Environmental Factors and Influence of Rumen and Hindgut Biogeography on Bacterial Communities in Steers

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