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Title: Determining the protective effects of Lactobacillus reuteri against enteropathogenic Escherichia coli infection
Author: Walsham, Alistair
ISNI:       0000 0004 6058 7990
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2016
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Enteropathogenic Escherichia coli (EPEC) are non-invasive foodborne diarrhoeal pathogens that are a leading cause of infant death in the developing world. As antibiotic resistance increases amongst pathogens, new treatments are required to reduce infant mortality. Probiotic bacteria could offer a solution, and Lactobacillus reuteri have been shown to alleviate diarrhoea and reduce EPEC colonisation in clinical studies. Here, we utilised mucus and non-mucus producing human intestinal epithelial cell lines as well as human duodenal biopsies to investigate the effects of L. reuteri ATCC PTA 6475 and ATCC 53608 on EPEC infection, with particular focus on pathogen adherence, host mucin production, and innate immune response. Short-term protection assays demonstrated that pre-incubation with an excess of L. reuteri inhibited EPEC epithelial binding, independently of secreted products and probiotic epithelial adhesion. Increased pre-incubation times enhancing L. reuteri adhesion reduced EPEC binding to HT-29 cells by ATCC PTA 6475. While this strain did not inhibit EPEC adhesion to LS174T cells, ATCC PTA 6475 significantly reduced cell to cell spread of EPEC, a characteristic which has not previously been described. In addition to reducing EPEC adherence, incubation with L. reuteri ATCC PTA 6475 increased MUC2 protein production in LS174T cells. In contrast, EPEC infection reduced MUC2 protein levels and this effect was diminished by co-incubation with ATCC PTA 6475, suggesting that L. reuteri protect against EPEC-mediated MUC2 degradation. L. reuteri also demonstrated anti-inflammatory characteristics, as ATCC PTA 6475 and ATCC 53608 inhibited EPEC-induced interleukin-8 protein expression in HT-29 cells. Taken together, our findings suggest that L. reuteri protects against EPEC infection by reducing pathogen binding and modulating host mucus production and inflammation. These effects are strain-specific and dependent on the host model system used. Therefore, the probiotic potential of L. reuteri strains needs to be carefully evaluated in relevant systems before application in clinical practice.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available