Microbiological and histological study of the gastrointestinal tract of germ-free mice infected with Helicobacter trogontum

Helicobacter spp. have been the focus of considerable research because of t he role of this genus in gastrointestinal diseases. We infected NIH germ-fr ee mice with Helicobacter trogontum, a recently described intestinal bacter ium of rats, in order to study the distribution of this bacterium in the ga strointestinal tract and the histopathological changes it can induce in thi s host. Sixteen mice were challenged with a single dose of H. trogontum (te st group) and killed one and six weeks after inoculation (eight animals at each point), Eight animals were challenged with 0.85% saline alone (control group) and killed at the same time points (four at each point). Fragments from the gastric and intestinal mucosa were obtained for microbiological an d histological examination. H. trogontum was isolated from the cecum and co lon of all test mice and also from the gastric mucosa of several of them. A ll infected animals presented histological changes in at least one region o f the bowel. Alterations in the gastric mucosa were also observed mainly in the six-week-infected group. The predominant histological change observed was a moderate diffuse inflammatory infiltrate of mononuclear cells in the lamina propria, often accompanied by a mild infiltration of polymorphonucle ar cells. Two animals presented focal infiltration of inflammatory cells in the liver, although no bacteria were found in the liver of any animal. H. trogontum is an intestinal species that is able to elicit inflammatory resp onses in other regions of the gastrointestinal tract such as the gastric mu cosa and the liver of gnotobiotic mice. (C) Elsevier, Paris.