Isolation and identification of a tick-borne salt and alkali tolerant bacterium Oceanobacillus oncorhynchi IMH

Abstract:

[Objective] In this study, an unknown bacterium was isolated from Dermacentor nuttalli-a dominant tick species in the area of Hulunbuir. Then we identified the bacterium by molecular biology. We also explored its pathogenicity. [Methods] First, through conventional morphological observation, physiological and biochemical analysis, drug sensitivity test, 16S rRNA gene sequence analysis and constructing phylogenetic tree, we confirmed the taxonomic status of the bacterium. Then we did pathogenicity experiment on mice. [Results] This bacterium was Gram-positive and grew well in high-salt medium (5% NaCl) and alkaline medium (pH 9), but its ability was limited to ferment sugar, instead it only used some sugar (Simon's citrate test showed positive results) to make aerogenesis but not acid. It is sensitive for individual chemicals like ciprofloxacin, and most antibiotics like neomycin, gentamicin, erythromycin and cefotaxime, whereas it was resistance to kanamycin and amoxicillin. From the analysis of the 16S rRNA gene sequence and the phylogenetic trees, we found that the homology of this bacterial strain and Oceanobacillus oncorhynchi from the GenBank database (GenBank:GQ121034.1) is over 99%. Besides, this bacterial strain shows incomplete hemolysis and no obvious pathogenicity was observed in Kunming mice 7 days after infection. [Conclusion] A tick-borne O. ncorhynchi strain was isolated, identified and named O. oncorhynchi IMH and registered in Genbank (No. LC213016.1), which enriched the relevant data in GenBank.