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Ecology and persistence of Escherichia coli O157:H7 in feedlot cattle and characterization of molecular mechanisms responsible for attachment

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dc.contributor.authorCarlson, Brandon Adolph, author
dc.contributor.authorBelk, Keith E., advisor
dc.date.accessioned2024-03-13T18:50:56Z
dc.date.available2024-03-13T18:50:56Z
dc.date.issued2009
dc.description.abstractStudies were conducted to elucidate the shedding dynamics and ecology of Escherichia coli O157:H7 in feedlot cattle. Feedlot cattle (N=788) were evaluated for E. coli O157:H7 shedding six times during the final 120 d of finishing. Fecal samples were analyzed for E. coli O157:H7 with IMS and confirmed with multiplex PCR. During the first two collections, where all 788 steers were samples, 39.8 and 33.6% of steers were shedding an E. coli O157:H7 isolate possessing eae, stxI, and stxII. Through subsequent sampling, 1% of steers were characterized as persistent E. coli O157:H7 shedders (PS) where as 1.4% of steers were never shedding a detectable amount of the organism. Molecular characterization of E. coli O157:H7 isolates obtained from PS (n=80) and transient E. coli O157:H7 shedders (n=52) revealed a diverse but closely related population of isolates and identified a predominant subtype that accounted for 53% of the isolates characterized that was not dependent (P > 0.05) on animal shedding status. Pathogenic potential of E. coli O157:H7 isolates representing different subtypes was delineated with a Caco-2 cell (intestinal epithelial cell line) attachment assay. There was an inverse relationship (P < 0.05) between genetic diversity and attachment efficacy; as diversity from the dominant subtype increased, ability to attach to Caco-2 cells diminished. Additional attachment assays were initiated to evaluate the influence of virulence genes upon E. coli O157's ability to attach to Caco-2 cells. E. coli O157 isolates without either stx, no stxI, and no stxII genes resulted in attachment abilities of 76.7, 65.5 and 57.7%, respectively; all of which were greater (P < 0.05) than an E. coli O157:H7 that was isolated from a food implicated in human disease and possessed both stx genes. Cytotoxicity assays were utilized to verify that differences in attachment efficacy, exhibited by E. coli O157 isolates of various virulence genotypes, were independent of cellular destruction.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.identifierETDF_Carlson_2009_3401032.pdf
dc.identifier.urihttps://hdl.handle.net/10217/237626
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.rights.licensePer the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users.
dc.subjectcytotoxicity
dc.subjectEscherichia coli O157:H7
dc.subjectfeedlot cattle
dc.subjectmicrobiology
dc.subjectanimal sciences
dc.subjectanimal diseases
dc.titleEcology and persistence of Escherichia coli O157:H7 in feedlot cattle and characterization of molecular mechanisms responsible for attachment
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineAnimal Sciences
thesis.degree.grantorColorado State University
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy (Ph.D.)

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