title: Characterization of Escherichia coli O157:H7 strains isolated from supershedding cattle.
abstract: Previous reports have indicated that a small proportion of cattle shedding high levels of Escherichia coli O157:H7 is the main source for transmission of this organism between animals. Cattle achieving a fecal shedding status of 10(4) CFU of E. coli O157:H7/gram or greater are now referred to as supershedders. The aim of this study was to investigate the contribution of E. coli O157:H7 strain type to supershedding and to determine if supershedding was restricted to a specific set of E. coli O157:H7 strains. Fecal swabs (n = 5,086) were collected from cattle at feedlots or during harvest. Supershedders constituted 2.0% of the bovine population tested. Supershedder isolates were characterized by pulsed-field gel electrophoresis (PFGE), phage typing, lineage-specific polymorphism assay (LSPA), Stx-associated bacteriophage insertion (SBI) site determination, and variant analysis of Shiga toxin, tir, and antiterminator Q genes. Isolates representing 52 unique PFGE patterns, 19 phage types, and 12 SBI clusters were obtained from supershedding cattle, indicating that there is no clustering to E. coli O157:H7 genotypes responsible for supershedding. While being isolated directly from cattle, this strain set tended to have higher frequencies of traits associated with human clinical isolates than previously collected bovine isolates with respect to lineage and tir allele, but not for SBI cluster and Q type. We conclude that no exclusive genotype was identified that was common to all supershedder isolates.
authors: U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska, USA. Terrance.Arthur@ars.usda.gov
authors: Terrance M
authors: TM
authors: Arthur
authors: Rafiq
authors: R
authors: Ahmed
authors: Margo
authors: M
authors: Chase-Topping
authors: Norasak
authors: N
authors: Kalchayanand
authors: John W
authors: JW
authors: Schmidt
authors: James L
authors: JL
authors: Bono
mesh_terms: D000818:Animals; D057138:Bacterial Shedding; D001434:Bacteriophage Typing / Q000662:veterinary; D001435:Bacteriophages / Q000235:genetics; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000235:genetics / Q000382:microbiology*; D015169:Colony Count, Microbial / Q000662:veterinary; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000235:genetics / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology; D060005:Genotyping Techniques / Q000662:veterinary; D015999:Multivariate Analysis; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D015995:Prevalence; D014481:United States / Q000453:epidemiology
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