Monitoring Escherichia coli O157:H7 in Inoculated and Naturally Colonized Feedlot Cattle and Their Environment

Abstract

On-farm methods of monitoring Escherichia coli O157:H7 were assessed in 30 experimentally inoculated steers housed in four pens over a 12-week period and in 202,878 naturally colonized feedlot cattle housed in 1,160 pens on four commercial Alberta feedlots over a 1-year period. In the challenge study, yearling steers were experimentally inoculated with 10(10) CFU of a four-strain mixture of nalidixic acid-resistant E. coli O157:H7. After inoculation, shedding of E. coli O157:H7 was monitored weekly by collecting rectal fecal samples (FEC), oral swabs (ORL), pooled fecal pats (PAT), manila ropes (ROP) orally accessed for 4 h, feed samples, water, and water bowl interface. Collection of FEC from all animals per pen provided superior isolation (P < 0.01) of E. coli O157:H7 compared with other methods, although labor and animal restraint requirements for fecal sample collection were high. When one sample was collected per pen of animals, E. coli O157:H7 was more likely to be detected from the ROP than from the FEC, PAT, or ORL (P < 0.001). In the commercial feedlot study, samples were limited to ROP and PAT, and E. coli O157:H7 was isolated in 18.8% of PAT and 6.8% of ROP samples. However, for animals that had been resident in the feedlot pen for at least 1 month, isolation of E. coli O157:H7 from ROP was not different from that from PAT (P = 0.35). Pens of animals on feed for <30 days were six times more likely to shed E. coli O157:H7 than were animals on feed for >30 days. However, change in diet did not affect shedding of the organism (P > 0.23) provided that animals had acclimated to the feedlot for 1 month or longer. Findings from this study indicate the importance of introduction of mitigation strategies early in the feeding period to reduce transference and the degree to which E. coli O157:H7 is shed into the environment.

Escherichia coli O157:H7 Strains That Persist in Feedlot Cattle Are Genetically Related and Demonstrate an Enhanced Ability To Adhere to Intestinal Epithelial Cells

“…Our data contribute to the growing body of evidence indicating that E. coli O157:H7 persists in cattle populations. More specifically, along with several previous studies (6,43,45,48,51), our study supports the conclusion that a given population of feedlot cattle appears to be colonized by a single predominant strain and a few closely related strains. The predominant PFGE subtype in our study was disseminated into each animal pen, was found on each sample collection date, and was shed by each PS animal on at least two consecutive sample collection dates.…”

Responses of Cattle to Gastrointestinal Colonization by Escherichia coli O157:H7

“…These alterations were associated with a quantifiable neutrophilic response. The microscopic examination was made in animals shedding bacterial numbers similar to those animals considered super-shedders in field studies (10,22,34). Similar lesions have been reported in weaned calves 4 days postchallenge (7).…”

Isolation of Escherichia coli 0157:H7 Strain from Fecal Samples of Zoo Animal

“…The seasonality of the incidence of E. coli O157:H7 in petting zoo animals, coupled with the increase in E. coli O157:H7 associated with food-borne illness during the summer months, suggests that environmental replication plays a key role in the epidemiology of infections [42, 43]. …”