A spp. Isolate from a Pac-Man Frog () Reveals Characteristics Departing from Classical Brucellae.

are highly infectious bacterial pathogens responsible for brucellosis, a frequent worldwide zoonosis. The genus has recently expanded from 6 to 11 species, all of which were associated with mammals; The natural host range recently expanded to amphibians after some reports of atypical strains from frogs. Here we describe the first in depth phenotypic and genetic characterization of a strains isolated from a frog. Strain B13-0095 was isolated from a Pac-Man frog () at a veterinary hospital in Texas and was initially misidentified as . We found that B13-0095 belongs to a group of early-diverging brucellae that includes strain BO1 and the -like strain BO2, with traits that depart significantly from those of the "classical" spp. Analysis of B13-0095 genome sequence revealed several specific features that suggest that this isolate represents an intermediate between a soil associated ancestor and the host adapted "classical" species. Like strain BO2, B13-0095 does not possess the genes required to produce the perosamine based LPS found in classical , but has a set of genes that could encode a rhamnose based O-antigen. Despite this, B13-0095 has a very fast intracellular replication rate in both epithelial cells and macrophages. Finally, another major finding in this study is the bacterial motility observed for strains B13-0095, BO1, and BO2, which is remarkable for this bacterial genus. This study thus highlights several novel characteristics in strains belonging to an emerging group within the genus. Accurate identification tools for such atypical isolates and careful evaluation of their zoonotic potential, are urgently required.