Helicobacter spp. Infection

A variety of Helicobacter spp. colonize the gastro­intestinal tracts of Syrian hamsters, including Helico­bacter aurati, Helicobacter cinaedi, Helicobacter cholecystitis, Helicobacter mesocricetorum, and a Helico­bacter sp.

Pathology

Helicobacter aurati was isolated from the stomach and cecum of adult hamsters with gastritis, and chronic gastritis with intestinal metaplasia has been noted in hamsters naturally infected with H. aurati and 2 other microaerobic species. An invasive adenocarcinoma at the pyloric-duodenal junction was observed in a ham­ster at the site of H. aurati-associated inflammation. Helicobacter cholecystus has been isolated from the gall bladder of hamsters with cholangiofibrosis, bile ductular hyperplasia, portal hepatitis, and centrilobular pancrea­titis. Spontaneous proliferative and dysplastic typhloco­litis associated with Helicobacter sp. infections has also been identified in aging hamsters. The agent genetically clustered closely with H. bilis. Lesions were most evident

FIG. 3.11. Cecum from a Syrian hamster with naturally occurring Helicobacter infection. There are multiple cystic areas (arrow) in the hyperplastic mucosa. Source: Nambiar et al. 2006. Reproduced with permission from SAGE Publications.

at the ileocecocolic junction and terminal colon. Muco­sal thickening and submucosal edema, hypertrophy of enterocytes, and hyperplasia of cells lining crypts were observed. Chronic inflammatory cell infiltrates in the lamina propria consisted primarily of lymphohistiocytic cells with a sprinkling of polymorphonuclear leukocytes (Figs. 3.11 and 3.12). Chronic hepatitis, portal fibrosis, biliary hyperplasia, and focal nodular dysplasia have also been found in aged hamsters infected with a Helicobacter spp. that clusters in the H. bilis clade. A round cell sarcoma and a histiocytic sarcoma were identified at the ileocecocolic junction in two of the affected animals. This Helicobacter sp. was also associated with hepatic

FIG. 3.12. Colon from a hamster with chronic colitis associated with Helicobacter infection. Note the hyperplasia of enterocytes lining crypts and the cellular infiltrate in the lamina propria. Source: Nambiar et al. 2006. Reproduced with permission from SAGE Publications.

portal fibrosis, which is a common sequel of enterohe- patic Helicobacter infections.