EXPERIMENTAL-INFECTION OF WISTAR RATS WITH GASTROSPIRILLUM-SUIS

In order to develop a model for the study of gastric spiral bacteria, and based on the observation that Wistar rats do not carry urease-posi tive spiral bacteria in their gastric mucosa, mucus from a pig natural ly colonised by 'Gastrospirillum suis' (an organism with I6S rDNA 99.5 % similar to that of 'G, hominis' type 1), was inoculated into 35 Wist ar rats (test group). Fourteen rats were given mucus taken from 'G, su is'-negative swine (control group). Five test animals and two controls were killed 1, 2, 4, 8, 12, 26 and 52 weeks after inoculation. 'G-sui s' was observed in the antral mucosa of all test rats but not in the g astric mucosa of any control animal. The number of organisms was high from the beginning of the infection and increased over the period of o bservation. The bacteria were seen deep in the gastric antral glands, especially in the advanced stages of infection. Histological study of two test rats killed 1 week after inoculation and of all rats killed f rom the second week after infection revealed the presence of a mild in flammatory response characterised by the infiltration of small numbers of mononuclear cells and scarce polymorphonuclear cells in the subgla ndular region of the antral mucosa. Lymphoid aggregates were observed in the antral mucosa of rats killed from 1 month onwards, and increase d in size and number over the period of infection. Control animals did not have any histological changes in the gastric mucosa. The natural transmission of the bacterium from rat to rat was also investigated. F ive noninoculated animals (contact group) and rats of the test group w ere maintained in the same cage and killed after 12 weeks. Two animals of the contact group showed slight infiltration of mononuclear cells in the antral mucosa, although they were not colonised by 'G, suis), a finding that supports the hypothesis of faecal-oral transmission of g astric Helicobacter spp. This animal model could be used not only to u nderstand different aspects of the relationship between spiral bacteri a and the gastric mucosa but also to obtain large numbers of the organ ism, free from other spiral bacteria to study some of its properties.