Helicobacter hepaticus strain ATCC 51449. This organism was found to be linked to an increasing incidence of liver tumors in mouse colonies at the National Cancer Institute in 1992. Normally it resides in the lower intestines, but it can cause chronic hepatitis. This organism has a similar urease gene cluster and cytolethal distending toxin as compared to Helicobacter pylori, but lacks other virulence factors such as the vacuolating cytotoxin and the cag pathogenicity island. However, it does contain a pathogenicity island that encodes proteins similar to those found in a type IV secretion system.