Abstract:

The bacterial isolation, identification and drug sensitivity of diseased Acrossocheilius hemispinus with skin ulceration, surface hemorrhage, swollen and bleeding liver were studied. The bacterial strain was isolated and purified from liver tissue of the diseased fish and injected intramuscularly into healthy Acrossocheilius hemispinus. Full-length sequences of 16S rDNA and gyrB gene were obtained by PCR amplification of pathogenic bacteria, while physiological and biochemical identification, virulent genes detection, and drug sensitivity study were also conducted. The isolated strain was numbered as AS0829L1, and the artificial infection experiments showed that pathogenic groups of 5×10¹⁰, 5×10⁹, 5×10⁸ CFU/mL could cause 100%, 100%and 28.6% mortality, respectively. The BLAST result indicated the sequences of 16S rDNA and gyrB were homologous to the corresponding sequence of Aeromonas veronii in Genbank, with homology as high as 99.93% and 99.34%, respectively. Comprehensive molecular biology, physiological and biochemical characteristics, virulence gene detection results demonstrated the separate strain was Aeromonas veronii bv.sobria. The drug sensitivity test showed the isolated strain was highly sensitive to 20 antibacterial drugs including cefuroxime, cefoperazone, gentamicin, neomycin, enrofloxacin and ofloxacin, moderate sensitive to 5 antibacterial drugs including carboxybenzillin, streptomycin, flufenicol, and resistant to 12 antibacterial drugs including penicillin, norfloxacin, erythromycin. In this study, the pathogen of the diseased Acrossocheilius hemispinus was identified and the drug sensitivity test of the isolated strain was carried out, which provided a research basis for the prevention and control of diseases in aquaculture production.

Key words: Acrossocheilius hemispinus, Aeromonas veronii bv. sobria, pathogenicity, drug sensitivity