title: Monitoring Seven Potentially Pathogenic Escherichia coli Serogroups in a Closed Herd of Beef Cattle from Weaning to Finishing Phases.
abstract: The goal of this study was to monitor Shiga toxin-producing Escherichia coli (STEC) serogroups and virulence genes in cattle (n = 30) originating from a closed herd. Fecal samples were collected (1) at weaning, (2) upon arrival to a feedlot, (3) after 30 days on feed (DOF), and (4) after 135 DOF. DNA was extracted from feces for detection of virulence and serogroup genes by polymerase chain reaction (PCR) and immunomagnetic separation and pulsed-field gel electrophoresis (PFGE) were performed to collect and subtype STEC isolates. The prevalence of each serogroup measured by PCR from weaning to 135 DOF was 23.3-80.0% for O26, 33.3-46.7% for O45, 70.0-73.3% for O103, 36.7-86.7% for O111, 56.7-6.7% for O121, 26.7-66.7% for O145, and 66.7-90.0% for O157. Total fecal samples positive for virulence genes were 87.5% for ehxA, 85.8% for stx1, 60.0% for stx2, 52.5% for eae, and 44.2% for the autoagglutinating adhesion gene, saa. The prevalence of each serogroup and virulence gene tended to increase by 135 DOF, with the exception of O121, stx2, and saa. The frequency of detection of some virulence genes was largely affected over time, most notably with saa and stx2decreasing, and eae increasing when cattle were transitioned to concentrate-based diets. PFGE analysis of O157 and O103 fecal isolates revealed dominant pulsotypes, but the presence of identical O103 isolates, which differed in virulence profiles. Overall, this study showed that fecal shedding of E. coli serogroups and virulence-associated genes are highly variable over time as cattle move from ranch to feedlot. To mitigate STEC, it is important to understand the factors affecting both prevalence of individual serogroups and the presence of virulence factors.
authors: 1 Agriculture and Agri-Food Canada, Lethbridge Research Centre , Lethbridge, Canada .
authors: Jennyka
authors: J
authors: Hallewell
authors: 2 Alberta Agriculture and Forestry, Agriculture Centre , Lethbridge, Canada .
authors: Tim
authors: T
authors: Reuter
authors: 2 Alberta Agriculture and Forestry, Agriculture Centre , Lethbridge, Canada .
authors: Kim
authors: K
authors: Stanford
authors: 3 Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre , London, Canada .
authors: Ed
authors: E
authors: Topp
authors: 1 Agriculture and Agri-Food Canada, Lethbridge Research Centre , Lethbridge, Canada .
authors: Trevor W
authors: TW
authors: Alexander
mesh_terms: D000416:Alberta; D000822:Animal Husbandry; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D017849:Animals, Inbred Strains; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D057138:Bacterial Shedding; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D004197:Disease Reservoirs / Q000382:microbiology; D062665:Epidemiological Monitoring / Q000662:veterinary; D004926:Escherichia coli / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification* / Q000502:physiology; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology; D005243:Feces / Q000382:microbiology; D005759:Gastroenteritis / Q000382:microbiology / Q000662:veterinary*; D008297:Male; D058889:Molecular Typing; D009919:Orchiectomy / Q000662:veterinary; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D014886:Weaning
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors
keywords: Shiga toxin–producing E. coli (STEC); cattle; detection; feces; multiplex PCR; non-O157