Grahamella in small woodland mammals in the U.K.: isolation, prevalence and host specificity.

Bacteria isolated from the blood of small woodland mammals were identified as members of the genus Grahamella. The prevalence of Grahamella infection among the 37 small mammals examined, detected by cultivation of blood samples, was 62%. This figure is somewhat higher than previous reports. Further characterization of the isolates, based on restriction enzyme analysis of the 16S rRNA gene, serological reactivity and DNA hybridization studies, revealed three distinct Grahamella species. One of the species was found in five different species of small mammal (Apodemus sylvaticus, A. flavicollis, Clethrionomys glareolus, Microtus agrestis and Neomys fodiens). All three species were found in M. agrestis, although there was no evidence of concurrent infection of an animal by more than one species of Grahamella. These observations demonstrate that Grahamella spp. are not host-specific, as previously thought, and that it is therefore invalid to name Grahamella spp. solely on the basis of the host in which they are observed.