Show simple item record

dc.contributor.advisorHill, Janeten_US
dc.contributor.advisorHarding, Johnen_US
dc.creatorCosta, Matheusen_US
dc.date.accessioned2016-03-23T12:00:18Z
dc.date.available2016-03-23T12:00:18Z
dc.date.created2016-02en_US
dc.date.issued2016-03-22en_US
dc.date.submittedFebruary 2016en_US
dc.identifier.urihttp://hdl.handle.net/10388/ETD-2016-02-2429en_US
dc.description.abstractThis thesis aimed to verify the causal association between "B. hampsonii" and the re-emergence of mucohaemorrhagic diarrhea in North American swine farms, to investigate the role of the intestinal microbiome as a predisposing factor for infection, to develop a porcine colon in vitro culture model and to apply this model in investigating early host-pathogen interactions. Two infection trials were conducted to determine the pathogenicity of "B. hampsonii" clade II and clade I. Weanling pigs were divided into control (n=6) and inoculated (n=12) groups. In each trial, pigs were inoculated with "B. hampsonii" clade II (tissue homogenate or pure culture) or clade I (pure culture) or sterile culture media. Animals were monitored for clinical signs of diarrhea and upon observation of bloody diarrhea they were necropsied for characterization of lesions. Fecal shedding of "B. hampsonii" was monitored throughout the trials using culture and quantitative real-time PCR. Pre and post-diarrhea fecal samples from the clade II infection trial were used to study the microbiome response to "B. hampsonii" infection and to determine if pre-inoculation microbiome composition differed between pigs that did or did not develop clinical disease. For in vitro model development, numerous factors associated with explant survivability in culture were investigated to develop a protocol for culture of porcine colon explants. The optimized model was used to study the first 12 hours of "B. hampsonii" clade II interaction with the host using a combination of histopathology and gene expression analysis. Pigs inoculated with "B. hampsonii" clade I (9/11) and clade II (9/12 and 8/12 in the tissue homogenate and pure culture experiments, respectively) developed mucohaemorrhagic diarrhea and colitis within 14 days of inoculation. In all trials, mucohaemorrhagic diarrhea was significantly more common in inoculated pigs than controls. No significant differences in richness, diversity or taxonomic composition distinguished the pre-inoculation microbiomes of affected or unaffected clade II inoculated pigs. After the development of diarrhea, the fecal microbiome of diarrheic pigs was more dense and had a had a lower Bacteroidetes:Firmicutes ratio when compared to inoculated but unaffected or control pigs. Cultured porcine colon explants displayed differentiated epithelium and crypts after 5 days in culture, while expressing GAPDH at a constant rate. For explants to thrive in vitro our results suggested the use of distal spiral colon, processed immediately after euthanasia, and cultured in an oxygen-rich gas mix with air-liquid culture interface in media containing antibiotics and antifungals. Explants exposed to "B. hampsonii" for 12 hours had a greater number of necrotic cells and thicker catarrhal exudate than control explants. Interaction of spirochaetes with the epithelium, necrotic cells and crypts was visible under optical microscopy, and a trend of increased expression of IFN-γ and e-cadherin in inoculated explants relative to control explants was observed. Taken together, results of this thesis demonstrate that "B. hampsonii" causes mucohaemorrhagic diarrhea in pigs and modulates their intestinal microbiome. The development of an in vitro infection model that replicates in vivo features facilitated the observation of the initial events in "B. hampsonii" interaction with the colon. When explants were exposed to "B. hampsonii" similar histological lesions to in vivo were observed. This system provides a powerful model for future studies of the pathogenesis of "B. hampsonii" and other enteric pathogens of pigs.en_US
dc.language.isoengen_US
dc.subjectBrachyspiraen_US
dc.subjectBrachyspira hampsoniien_US
dc.subjectpathogenesisen_US
dc.subjectpathophysiologyen_US
dc.subjectswine dysenteryen_US
dc.subjectcolitisen_US
dc.subjectmucohaemorrhagic diarrheaen_US
dc.subjectdiarrheaen_US
dc.subjectorgan explanten_US
dc.subjectin vitro organ cultureen_US
dc.subjectmicrobiomeen_US
dc.subjectspirocheteen_US
dc.subjectcolonic diarrheaen_US
dc.title"Brachyspira hampsonii" associated diarrhea in pigs: virulence assessment and host-pathogen interactionsen_US
thesis.degree.departmentVeterinary Microbiologyen_US
thesis.degree.disciplineVeterinary Microbiologyen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US
dc.type.materialtexten_US
dc.type.genreThesisen_US
dc.contributor.committeeMembervan Kessel, Andrewen_US
dc.contributor.committeeMemberDumonceaux, Timothyen_US
dc.contributor.committeeMemberMisra, Vikramen_US
dc.contributor.committeeMemberLoewen, Matthewen_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record