Abstract

A bacterial disease was reported from cultured loach Misgurnus anguillicaudatus in China. Symptoms included haemorrhages at the body surface (including base of fin, head, mouth, and abdomen), ulceration of muscle, and high-level mortalities. The dominant bacterial colonies were isolated in nutrient agar from different infected body parts and confirmed the pathogenicity by challenge experiments. The 3 strains (NQ1-3) were randomly selected and characterized phenotypically and genotypically. Biochemically, the 3 strains showed properties and biochemical characteristics similar toVibrio cholerae. Phylogenetic analysis of the 16S rRNA gene (GenBank accession No. JF939043) and 3 housekeeping genes, RNA polymerase a-chain (rpoA, GenBank accession No. JF939042), recombination repair protein (recA, GenBank accession No. JF939045) and DNA gyrase B subunit (gyrB, GenBank accession No. JF909344) of strain (NQ1) exhibited high similarity to those of V. cholerae from GenBank. The 3 strains (NQ1-3) were positive for toxR, lolB (previously called hemM) and rtxA (presumptive cytotoxin) genes, potential virulence factors. To sum up, the isolated strains were confirmed as V. cholerae on the basis of phenotypic characteristics, phylogenetic analysis of the 16S rRNA gene and three housekeeping genes, as well as potential virulence factors studies. The susceptibility of isolates to 28 antimicrobial agents was determined, NQ1 were found to be sensitive to some of the drugs tested, including carbenicillin, azlocillin, cefoperazone, ceftazidime, ceftriaxone, cephradine, azithromycin, lomefloxacin, levofloxacin, enoxacin, norfloxacin, neomycin, streptomycin, doxycycline, tetraecycline, and minomycin.

Key words: Misgurnus anguillicaudatus, Vibrio cholerae, housekeeping genes, ulcer disease.