IntroductionCold-blooded hosts, particularly exotic frogs, have become a newly recognized reservoir for atypicalBrucellaspecies and strains worldwide, but their pathogenicity to humans remains largely unknown. Here we report the isolation and molecular characterization of aB. inopinatastrain (FO700662) cultured from clinical samples taken from a captive diseased White’s Tree Frog (Litoria caerulea) in Switzerland. The isolation ofB. inopinatafrom a frog along with other reports of human infection by atypical Brucella raises the question of whether atypical Brucella could pose a risk to human health and deserves further attention.MethodsThe investigations included histopathological analysis of the frog, bacterial culture and in-depth molecular characterization of strain FO700662 based on genome sequencing data.Results and DiscussionOriginally identified asOchrobactrumbased on its rapid growth and biochemical profile, strain FO700622 was positive for theBrucella-specific markersbcsp31andIS711. It showed the specific banding pattern ofB. inopinatain conventional Bruce-ladder multiplex PCR and also had identical 16S rRNA and recA gene sequences asB. inopinata. Subsequent genome sequencing followed by core genome-based MLST (cgMLST) analysis using 2704 targets (74% of the total chromosome) revealed only 173 allelic differences compared to the type strain ofB. inopinataBO1T, while previously considered the closest related strain BO2 differed in 2046 alleles. The overall average nucleotide identity (ANI) between the type strain BO1Tand FO700622 was 99,89%, confirming that both strains were almost identical. InsilicoMLST-21 and MLVA-16 also identified strain FO700662 asB. inopinata. The nucleotide and amino acid-based phylogenetic reconstruction and comparative genome analysis again placed the isolate together withB. inopinatawith 100% support. In conclusion, our data unequivocally classified strain FO700622, isolated from an exotic frog, as belonging toB. inopinata.