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Title: The aetiology of the proliferative enteropathies.
Author: McOrist, S.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1988
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The entezopathogenicity and antigens of Campylobacter-like organisms and Campylobacter app associated with the proliferative enteropathies were investigated. Two gnotobiotic pigs exposed orally to a filtered suspension of intestinal mucosa designated 284/86 from a naturally infected pig subsequently developed lesions of proliferative enteritis. Culture of the successful mucosal inoculum only revealed a moderate number of C. coli, however an apparently greater number of Campylobacter-like organisms was evident in smears of this inoculum. The pathogenesis of porcine proliferative enteritis was clearer from the results of this study. Ten days after infection, curved bacilli had colonised the ileal and large intestinal crypts. Attachment and entry of Campylobacter-like organisms into crypt enterocytes was also evident, with some proliferation of both bacteria within cells and of the enterocytes themselves. Twenty days after infection there was similar intracellular colonisation of bacteria and proliferative activity, although no luminal bacteria were evident. A moderate sub-acute inflammatory reaction was evident throughout. Conventional hamsters dosed with C. jejuni developed varying degrees of localised acute intestinal inflammation. Hamsters dosed with C. hyointestinalis or C. cola did not develop any lesions. Lesions of proliferative enteritis were detected in hamsters dosed with porcine tissue 284/86. Numerous intra-cytoplasmic Campylobacter-like organisms were detected within enterocytes in affected portions of intestine. Weanling hamsters this proved to be susceptible to the agent of porcine proliferative enteritis by cross-species transmission. Whole cell antigen preparations were made of various Camoylobacter sp. -Indirect immunofluorescence assays incorporating rabbit antisera to each Campylobacter sp gave specific endpoints for each antiserum of 1: 160 to 1: 320. Rabbit antisera prepared to Campylobacter-like organisms partly purified from proliferative enteritis mucosa, by a homogenisation and filtration technique, also gave specific reactions in this assay, up to 1: 610. Intracellular Campylobacter-like organisms were also compared in gel electrophoresis protein profiles and immunoblotting reactions to Campylobacter spp. The intracellular organisms tested had a distinctive protein profile dissimilar to the profiles of the known Campylobacter spp. In immunoblotting reactions, each of the Camoylobacter sp antisera reacted strongly with homologous antigens, but none reacted with Camcylobacter-like organisms prepared from lesions, except for a minor reaction seen with one serum. Similarly antisera to Campylobacter-like organisms showed a strong reaction to 25K to 27K components of homologous antigens, with only minor reactions to various other components of the cultivated Campylobacter app. Therefore it is likely that the intracellular Campylobacter-like organisms have a distinctive antigenic profile and that the 25 and 27K components are major antigenic components. Mouse monoclonal antibodies were produced that were apparently specific to the intracellular Camoylobacter-like organisms. Immunoblotting results showed that these antibodies only bound to a 251 to 27K outer membrane component present in the intracellular organisms. Reactions with this component could not be detected in assays with normal pig intestine, or Camoylobacter sp antigen. Restriction endonuclease digestion of Camoylobacter sp with Bgl II gave suitably resolved DNA fragments of between 2kb and 25kb. Patterns obtained with Bgl II digestion of Camoylobacter sp were dissimilar to those of Camoylobacter-like organisms, and each Camoylobacter sp had a characteristic distinct pattern. Digestion of DNA from porcine tissue samples with Bgl II produced a diffuse smear of fragmented DNA bands between 0.5 and19kb, with no recognizable "ladder" effect. The genome of the Carylobacter-like organisms within enterocytes in proliferative enteritis therefore is different to that of known Camoylobacter spp associated with the disease. This suggests that the differences in antigenic structures between these bacteria axe due to genetic differences. Only a limited number of strains were examined. Looking at the evidence provided by this study, the overall tenor of the results suggests that the intracellular organisms could be a separate, new species of Camp lobacter. If indeed the intracellular organisms are a single, new Cammylobacter PGS/ABST ecies, then a new name may be proposed, such as "C. intracellulare". Verifica nthis side Oni of the validity of such a proposal would require further DNA studies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Enteritis in mammals Veterinary medicine Microbiology Molecular biology Cytology Genetics