Investigation of strategies to protect against harmful bacteria – mucosa interaction in crohn’s disease and other diarrhoeal diseases

Knight, Paul
Investigation of strategies to protect against harmful bacteria – mucosa interaction in crohn’s disease and other diarrhoeal diseases. Doctor of Philosophy thesis, University of Liverpool.

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The presence and replication of E.coli within Crohn’s Disease (CD) tissue has been confirmed by multiple authors and is hypothesised to be pivotal in the development of CD. In this thesis, quantification of E.coli bacteria within endoscopic biopsies has been achieved with high efficiency, sensitivity and reproducibility using PCR plasmid technology, and the technique’s utility demonstrated by quantifying E.coli within the biopsies of CD patients in clinical relapse and remission as well as within the first lesions present in CD relapse, aphthous ulcers. These studies showed some interesting correlations with clinical, macroscopic, and histological data, obtained during a clinical trial of soluble plantain fibre supplementation for prevention of relapse in CD. These included increased quantities of E.coli in tissues from the mucosa of patients in clinical relapse whose ileum was macroscopically normal yet histologically inflamed, and significant falls in the quantities of E.coli over time in the biopsy tissues of patients who were in clinical remission. The ability of a specific group of E.coli, the adherent invasive E. coli (AIEC), to replicate within macrophages, is increasingly perceived to be fundamental in CD pathogenesis. The replication of E.coli within the phagolysosomes of macrophages is implicated in the release of pro-inflammatory cytokines, granuloma formation, and the consequent mucosal injury seen in CD. The pharmacological inhibition of AIEC replication in this work within murine macrophage tissue in vitro by the immunosuppressive azathioprine and its active metabolite 6-thioguanine as well as by the antibiotic ciprofloxacin at clinically relevant concentrations is supportive of this central hypothesis, and also suggests new treatment combinations that might be trialled in active CD. Interestingly and unexpectedly the steroid hydrocortisone also inhibited AIEC replication within macrophages, suggesting that sepsis-related complications seen with steroid use clinically may be related to its effects on neutrophil recruitment, rather than on phagocytic killing of bacteria. The diarrhoeal pathogens EPEC, ETEC, and C. difficile represent a large disease burden in terms of infantile, travellers’, and antibiotic-associated diarrhoea respectively with C. difficile also sometimes implicated in the exacerbation of CD. Plantain (banana) non starch polysaccharide (NSP) has previously been demonstrated to inhibit AIEC adhesion to mucosal tissues, and this work demonstrates the inhibition of the adherence of ETEC and C. difficile to intestinal cells in vitro with two different modalities, using concentrations of soluble plantain fibre that are readily achievable in the distal intestinal lumen. Previous work on AIEC inhibition with plantain was confirmed, whilst oat fibre and apple pectin did not significantly inhibit ETEC adherence. EPEC was not inhibited by plantain fibre, which may be due to its unique epithelial interaction. These foodstuffs, if prepared as suitable supplements, may offer new prophylactic therapeutic interventions for global and institutional diarrhoeal illness following appropriate clinical trials.

Item Type: Thesis (Doctor of Philosophy)
Additional Information: Date: 2011-12 (completed)
Uncontrolled Keywords: Crohn's macrophages plantain diarrhoea PCR
Divisions: Faculty of Health and Life Sciences > Institute of Systems, Molecular and Integrative Biology
Depositing User: Symplectic Admin
Date Deposited: 10 Aug 2012 10:54
Last Modified: 16 Dec 2022 04:36
DOI: 10.17638/00005833