Helicobacter ganmani sp. nov., a urease-negative anaerobe isolated from the intestines of laboratory mice

Spiral bacteria were isolated from the intestines of laboratory mice during a study examining the presence of Helicobacter species and other spiral organisms naturally infecting mice maintained at four different animal facilities in Sydney, Australia. One group of 17 isolates, cultured from mice from three of the four facilities, were found to be helicobacters but did not fall within any of the 18 currently recognized species. These isolates were unusual in that they only grew anaerobically at 37 degrees C and were incapable of growth under microaerobic conditions. Like Helicobacter rodentium, isolates possessed single, bipolar, unsheathed flagella and were urease-negative. They were positive for oxidase and reduced nitrate to nitrite but did not hydrolyse hippurate or indoxyl acetate, grew on charcoal agar and were resistant to cephalothin. 16S rDNA sequences from four strains were determined and found to be identical to one another. H. rodentium was the most closely related species in terms of 16S rDNA sequence similarity (98.2%). Numerical analysis of whole-cell proteins by SDS-PAGE for nine isolates was carried out with a comparison to all known Helicobacter species, including newly determined profiles from three H. rodentium strains. The new isolates were clearly differentiated from H. rodentium and other Helicobacter spp. On the basis of this data, including genetic, biochemical and protein analysis, it is proposed that these isolates belong to Helicobacter ganmani sp. nov. (type strain CMRI H02T = CCUG 43526T = CIP 106846T).