To develop probiotics for Helicobacter pylori infection, we screened 203 Latobacillus strains. Lactobacillus gasseri OLL2716 (LG21) was selected as the most effective strain to inhibit the growth of H. pylori by in vitro tests and animal study. We examined the effects of yogurt containing LG21 on H. pylori infection in humans. The intake of yogurt containing LG21 both decreases the number of H. pylori and also reduces mucosal inflammation. LG21 was shown to be effective as a probiotic for H. pylori infection.

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During the last one-half century we have witnessed a continuous evolution of the concept of microbial factors in the pathogenesis of IBD, an evolution that has never relinquished the involvement of such factors in gut inflammation, but has generated rather different views and variable degrees of enthusiasm for the importance of microbes in IBD. The failure to isolate classical or atypical microorganisms in CD or UC tissues made IBD investigators to look for answers in the field of immunology, looking for evidence of specific immune reactivity markers against bacterial antigens. The answers obtained were not satisfactory, and the search moved on to mycobacteria and viral agents with similar results. At the time that our understanding of mucosal immunity has already lead to the creation of the concept of “physiological” and pathological mucosal inflammation, genetic manipulations started to generate animals whose unexpected outcome was the development of colitis which is strictly dependent on the presence of an enteric flora. This fundamental observation was followed by the demonstration that in IBD there is a loss of immunological tolerance against the normal enteric flora and clinical trials showing that antibiotics and probiotics may be therapeutically beneficial in IBD patients, all of which ended up with the creation of the present view that the normal enteric flora is an essential component of IBD pathogenesis. This view still requires solidification through the definition of the relevant cellular and molecular pathways, and at the same time clinical studies must go on and explore how best modulate the gut flora and interfere with its proinflammatory potential in genetically susceptible individuals.

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The large bowel epithelium lives in a symbiotic relationship with millions of bacteria. These bacteria ferment dietary fibre to the short chain fatty acids, of which butyrate appears to be the most important. A technique was developed which allowed the rate of oxidation of fuel sources to be measured in colonic mucosal biopsies. This combined manometric methods with radiotracer technology. In normal colonic mucosal biopsies the rate of oxidation of butyrate was far greater than glutamine and in turn glucose. In patients with quiescent ulcerative colitis there was a significant defect in the mucosal ability to oxidize butyrate. Following on from this in vitro experiment, an in vivo experiment was performed, studying the rate of metabolism of a butyrate enema, in patients with quiescent colitis compared to controls. This showed no significant defect in whole body butyrate metabolism as measured by the production of ¹³CO₂ from ¹³Cbutyrate. Hydrogen sulphide, a bacterial metabolite, was found to inhibit butyrate metabolism in the colonic cell culture line HT 29. However, this inhibition was prevented by the presence of glucose. Immunological studies found that butyrate, in physiological concentrations, inhibited phytohaemaglutinin induced proliferation of peripheral lymphocytes. Butyrate also induced expression of CD69 but not CD25. These studies show that butyrate, as well as being a major fuel source for the colonic epithelium, has an immunosuppressant effect on lymphocytes. This may play a major part in maintaining the homeostasis between the colonic epithelium and the colonizing bacteria.

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Survival responses to aerobic stress in the Campylobacter jejuni are highly influenced by preculturing conditions in either microaerobic or anaerobic environments before the stress is induced. In anaerobically precultured cells, culturability was maintained longer than that in microaerobically precultured cells under aerobic conditions, without significant concomitant damage to cellular components by aerobic stress, although the culturability finally fell below the level of detection. These results suggest a possibility that the survival of C. jejuni in natural aerobic environments is highly influenced by the environmental conditions, such as varied oxygen partial pressure, where the bacterium has resided.

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