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Molecular and culture based investigation of the equine intestinal microflora

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Title: Molecular and culture based investigation of the equine intestinal microflora
Author: Schoster, Angelika
Department: Department of Clinical Studies
Advisor: Arroyo, Luis G.Weese, J. Scott
Abstract: The equine intestinal microflora has an enormous impact on health and performance, but is poorly understood. As many bacteria are unculturable, molecular methods have been adapted to study its composition, but are incompletely investigated. 'Clostridium difficile, C. perfringens' and ' Salmonella' are important equine enteric pathogens, but little epidemiologic information is available. This research addressed the use of terminal restriction fragment length polymorphism (TRFLP) to assess the equine intestinal microflora. Also, new epidemiologic data on enteric pathogens was obtained, including prevalence in different intestinal compartments and longitudinal carriage over the course of one year. Ingesta were collected from intestinal compartments of euthanized horses. TRFLP and Dice similarity indices were used to assess variation. Considerable diversity in the intestinal microflora both within and among horses was identified. TRFLP showed good repeatability, but lacked discriminatory power; therefore its usefulness is questionable. To determine the prevalence of 'C. difficile' and ' C. perfringens' in different gastrointestinal compartments, selective cultures of ingesta samples from euthanized horses were performed. Toxigenic ' C. difficile' was isolated from 14/135 (10.3%) samples from 8/15 (53.3%) horses. Multiple compartments were positive in four horses, and >=1 ribotype was always present. Multiple strains of 'C difficile' were identified in some individuals suggesting transient passage rather than colonization. ' C. perfringens' Type A was present in 1/135 (0.7%) samples. To investigate longitudinal epidemiology, feces were collected monthly from 25 horses for one year. Selective cultures were performed for ' C. difficile, C. perfringens, Salmonella' and 'Escherichia coli. C. difficile' isolates were molecularly characterized and ' E. coli' antimicrobial susceptibility profiles determined. Toxigenic ' C. difficile' was isolated from 15/275 (5.45%) samples from 10/25 (40%) horses. Four horses were positive in multiple months, differing ribotypes were found in three (75%). 'C. perfringens' and 'Salmonella ' were not detected. 'E. coli' was isolated from 232/300 (77%) fecal samples. Resistance to >=1 and >=3 antimicrobials was present in 31/232 (13.4%) and 6/232 (2.6%) of samples respectively. Changes in ' C. difficile' ribotypes over time suggest that horses are short-term carriers. Therefore healthy equids appear to be a minor reservoir for this potential human and animal pathogen and for antimicrobial resistance.
URI: https://hdl.handle.net/10214/25038
Date: 2011
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