Visuvanathan, Shikandhini;
(1991)
The characterisation of pleomorphic acid fast organisms isolated from patients with inflammatory bowel disease.
Doctoral thesis (M.D), UCL (University College London).
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Abstract
The experimental work done consists of three components. First, the isolation of extremely slow growing pleomorphic acid fast organisms (PAFOs) from mesenteric lymph nodes of cases of Crohn's disease (17/25) and Ulcerative Colitis (11/15). This is statistically significant compared to controls (3/17). Second, the viability of the organisms was proved by their repetitive re-isolation on subculture, and the organisms were shown to have DNA. Similar organisms previously isolated and maintained since 1976 were viable after several years in culture. This high isolation rate of apparently identical organisms from Ulcerative colitis (UC) as well as Crohn's disease (CD) has not been reported by other groups. The third aim of this thesis was to characterise the acid-fast organisms to determine if the organisms belonged to the genus Mycobacterium and were indeed homogeneous. Electron microscopy showed that the isolates had a cell wall. An extremely useful DNA extraction technique applicable to all bacteria, mycobacteria and IBD-derived acid fast organisms tested is described. El/33 PAPO derived DNA samples hybridised with probes prepared from the EWA of Mycobacterium kansasii and Mycobacterium paratuberculosis on dot blot hybridisation. Cloned probes prepared from PAFO did not show hybridisation with a specific mycobacterial species. Investigation for the presence of tuberculostearic acid by gas chromatography and mass spectrometry suggested its presoice in 13/16 CD cultures, 6/10 UC cultures and 3/8 control cultures which grew the acid-fast organisms. The relationship of the bacteria to mycobacteria were further investigated by protein analysis, analysis for the 30 kDa Fibronectin binding antigen and mycolic acid analysis. A few CD cultures showed the presence of the 30 kDa antigen and mycobacterial mycolates. Despite attempts to find alternative culture methods for higher yields, Robertson's cooked meat broth remains overall the best available medium for the growth of these organisms. In conclusion, the organisms show many mycobacterial markers. The association of these bacteria with IBD is certain but their aetiological role remains unproven. The work has been brought forward to a stage where DNA has been amplified for nucleotide sequencing and a long term study in nude mice has been initiated in an attempt to establish an animal model.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | M.D |
| Title: | The characterisation of pleomorphic acid fast organisms isolated from patients with inflammatory bowel disease |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10123349 |
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