Occurrence of Helicobacter species other than H. hepaticus in laboratory mice and rats in Sweden

The aim of this study was to determine which Helicobacter species other than H. hepaticus colonize laboratory mice and rats in Sweden. We analyzed 63 intestinal samples from mice and 42 intestinal samples from rats by partial 16S rDNA sequence analysis. Previously these samples had been found positive for Helicobacter species but negative for H. hepaticus in a polymerase chain reaction screening assay at the National Veterinary Institute in Sweden. H. ganmani, H. typhlonius, H. rodentium, an uncharacterized Helicobacter species ('hamster B'), and a possibly novel species were detected in mice. The possibly novel species was most closely related to H. apodemus strain YMRC 000216 (98.3% sequence similarity). Two different Helicobacter species were detected in rats: H. ganmani and H. rodentium. H. ganmani colonization of rats has not previously been reported.