12 January - 20 June 2016

Study carried out to examine how E.coli bacteria colonise our gut

25 March 2015

New research conducted at the University of East Anglia has looked into the relationship of the bacterium enterohemorrhagic E.coli (EHEC) and the lining of the colon. EHEC is a food borne pathogen that is a major cause of bacterial diarrhoea in the developed world. The bacteria mainly thrive in the gut of cattle and are transferred to humans either via the consumption of undercooked beef, through fruit and vegetables that have been contaminated or through direct contact with the animals. In extreme cases, EHEC infections can lead to acute gastroenteritis (inflammation of stomach and intestines), hemorrhagic colitis (an extreme complication leading to inflammation of the colon) and hemolytic uremic syndrome (HUS). The latter two are thought to be associated with the release of bacterial Shiga toxins (Stxs) that primarily affect the kidneys and the central nervous system. This study aimed to look at the adherence of EHEC to colonic epithelium by using in vivo organ culture (IVOC) of colonic biopsy samples as well as polarised T84 colon carcinoma cells. The adhesion of EHEC to the colon is thought to be due to the formation of attaching and effacing lesions (A/E).

The study of the adhesion to the colon was investigated by infecting terminal colonic biopsy samples with various strains of bacteria (EDL933, Walla-1 and H0-7184-0336) and leaving them for 8 hours. The samples were then analysed via IVOC at 20% oxygen levels. The study also looked into the EHEC adherence phenotype to the T84 colon carcinoma cell by using confluent cell monolayers that were grown on coverslips and infected with Stx-negative strain of TUV93-0. The adherence phenotype was then investigated using fluorescent actin staining and scanning electron microscopy. A look into the effect of the oxygen levels in the environment on the effect of the adhesion was also performed using IVOC at high (95%) and low (20%) levels of oxygen.

The results of the experiments showed that EHEC forms typical A/E lesions on the human colon during human infection and are probably a major contributor to colonic pathology. Results also showed that the increased level of oxygen suppressed EHEC adhesion and therefore the A/E lesions on the colon. The investigation of the adhesion phenotype to polarised T84 showed that it did not form typical A/E lesions.
The results of this study give a first look at how EHEC manifests in the colon, and will hopefully help in the development of new medication and treatments for EHEC infections in the future.

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