A Gram-negative, motile bacterium with bipolar sheathed flagella (one at each end) was isolated from the stomach of house musk shrews (Suncus murinus) with chronic gastritis. The isolates grew at 37 degrees C under microaerophilic conditions, but not under aerobic conditions; rapidly hydrolyzed urea; were catalase, oxidase, alkaline phosphatase, and arginine aminopeptidase positive; reduced nitrate to nitrite; and were resistant to cephalothin and nalidixic acid, but sensitive to tetracycline, erythromycin, and chloramphenicol. This bacterium was found on gastric epithelial cells by electron microscopy. In addition, a coccoid form of the bacteria was found in vacuoles formed in the epithelial cells of some of the house musk shrews tested. These results, including 16S rRNA gene sequence analysis, strongly suggested that this bacterium should be classified as a novel Helicobacter species. It is proposed that this bacterium should be called "Helicobacter suncus.".