Escherichia coliO26 in Feedlot Cattle: Fecal Prevalence, Isolation, Characterization, and Effects of anE. coliO157 Vaccine and a Direct-Fed Microbial

Abstract

Escherichia coli O26 is second only to O157 in causing foodborne, Shiga toxin-producing E. coli (STEC) infections. Our objectives were to determine fecal prevalence and characteristics of E. coli O26 in commercial feedlot cattle (17,148) that were enrolled in a study to evaluate an E. coli O157:H7 siderophore receptor and porin (SRP(®)) vaccine (VAC) and a direct-fed microbial (DFM; 10(6) colony-forming units [CFU]/animal/day of Lactobacillus acidophilus and 10(9) CFU/animal/day of Propionibacterium freudenreichii). Cattle were randomly allocated to 40 pens within 10 complete blocks; pens were randomly assigned to control, VAC, DFM, or VAC+DFM treatments. Vaccine was administered on days 0 and 21, and DFM was fed throughout the study. Pen-floor fecal samples (30/pen) were collected weekly for the last 4 study weeks. Samples were enriched in E. coli broth and subjected to a multiplex polymerase chain reaction (PCR) designed to detect O26-specific wzx gene and four major virulence genes (stx1, stx2, eae, and ehxA) and to a culture-based procedure that involved immunomagnetic separation and plating on MacConkey agar. Ten presumptive E. coli colonies were randomly picked, pooled, and tested by the multiplex PCR. Pooled colonies positive for O26 serogroup were streaked on sorbose MacConkey agar, and 10 randomly picked colonies per sample were tested individually by the multiplex PCR. The overall prevalence of E. coli O26 was higher (p<0.001) by the culture-based method compared to the PCR assay (22.7 versus 10.5%). The interventions (VAC and or DFM) had no impact on fecal shedding of O26. Serogroup O26 was recovered in pure culture from 23.9% (260 of 1089) of O26 PCR-positive pooled colonies. Only 7 of the 260 isolates were positive for the stx gene and 90.1% of the isolates possessed an eaeβ gene that codes for intimin subtype β, but not the bfpA gene, which codes for bundle-forming pilus. Therefore, the majority of the O26 recovered from feedlot cattle feces was atypical enteropathogenic E. coli, and not STEC.

Genetic Diversity and Pathogenic Potential of Attaching and Effacing Escherichia coli O26:H11 Strains Recovered from Bovine Feces in the United States

“…Furthermore, this observed high level of diversity is interesting given that the strains investigated here originated from a limited population of cattle and were isolated over a short period of time (32). This high level of genetic diversity contrasts with data for O157: H7, in which more homogeneity was previously observed with regard to virulence profiles within this E. coli serotype (34,51).…”

“…The strains investigated in this study (n ϭ 178) were isolated from the feces of U.S. feedlot cattle. Strains originated from fecal samples collected between May and July 2011 from a study involving 17,148 cattle housed in 40 pens at a commercial feedlot in the Midwest (32). There is no known association of these strains with any human illness.…”

Virulence Gene Profiles and Clonal Relationships of Escherichia coli O26:H11 Isolates from Feedlot Cattle as Determined by Whole-Genome Sequencing

“…The serotypes of cattle O26:H11/H Ϫ strains were determined previously by PCR assay for the wzx O26 and fliC H11 genes; all the strains were O26, although several strains possessed an undetermined H antigen (20). In silico serotyping confirmed the lack of integrity of the H11 marker (fliC H11 ) in the strains with the unknown H antigen (4271-C, 4822-A, and 4848-A-B).…”

“…The strains were isolated from cattle feces in a commercial feedlot located in the Midwest (19). The isolation procedure included enrichment of the feces in E. coli broth, immunomagnetic separation (IMS) with O26-specific IMS beads, and plating on selective medium, followed by confirmation of the presumptive isolate by a multiplex PCR targeting the O26 wzx gene (wzx O26 ) and the three major virulence genes, stx 1 , stx 2 , and eae (20). The strains were stored on tryptone soy broth containing glycerol at Ϫ70°C until further use.…”

OMV-based vaccine formulations against Shiga toxin producingEscherichia colistrains are both protective in mice and immunogenic in calves

“…47 While most lines of research on veterinary vaccines are aimed exclusively at the O157:H7 serotype, available commercial vaccines have not proven effective against non-O157 strains, in the field. 48 , 49 The multi-antigenicity of OMV-based formulations vaccine could bring an opportunity for cross-protection against different serotypes. This important aspect will also be addressed in future experiments.…”