Helicobacter typhlonius sp. nov., a Novel Murine Urease-Negative Helicobacter Species

Abstract

Over the past decade, several Helicobacter species have been isolated from rodents. With the advent of PCR for the diagnosis of infectious agents, it has become clear that several previously uncharacterized Helicobacter species also colonize rodents. In this report, we describe a novel urease-negative helicobacter, Helicobacter typhlonius sp. nov., which was isolated from colonies of laboratory mice independently by two laboratories. Infection of immunodeficient mice by this bacterium resulted in typhlocolitis similar to that observed with other helicobacter infections. H. typhlonius is genetically most closely related to H. hepaticus. Like H. hepaticus, it is a spiral bacterium with bipolar sheathed flagella. However, this novel species contains a large intervening sequence in its 16S rRNA gene and is biochemically distinct from H. hepaticus. Notably, H. typhlonius does not produce urease or H(2)S nor does it hydrolize indoxyl-acetate. Compared to other Helicobacter species that commonly colonize rodents, H. typhlonius was found to be less prevalent than H. hepaticus and H. rodentium but as prevalent as H. bilis. H. typhlonius joins a growing list of helicobacters that colonize mice and are capable of inducing enteric disease in various strains of immunodeficient mice.

FIG. 1

Phylogenetic tree of members of the genera Helicobacter, Campylobacter, “Flexispira,” Wolinella, and Arcobacter based on 16S ribosomal DNA sequences and prepared by using the neighbor-joining method. Phylogenetic distances between bacteria are calculated by totaling horizontal branches between bacteria. Bar, 1 nucleotide substitution per 100 nucleotides.

FIG. 2

Negatively stained preparation of H. typhlonius MU 96-1 demonstrating single sheathed bipolar flagella and no periplasmic fibers. Bar, 1 μm.