Isolation and Identification of Aeromonas hydrophila Strain X1 from Acipenser baerii and Its Antibiotic Sensitivity

Abstract:

A pathogenic bacterial strain X1 was isolated from Siberian sturgeon (Acipenser baerii) suffering with bacterial septicemia. The 50% lethal concentration (LC50) of strain X1 was 5.62×105 CFU/mL, which showed that strain X1 was rather strong virulent to Acipenser baerii. Strain X1 was gram negative and 1.0 μm~1.2 μm × 2.1 μm~2.4 μm in size with peritrichous flagella, and had β-hemolytic activity on rabbit blood agar. By means of ATB expression identification and 16S rDNA sequence analysis, strain X1 was identified as Aeromonas hydrophila (locus number: EU669667), which was the closest relative to Aeromonas hydrophila strain ATCC35654 (locus number: X74676.1) with 99% homology. In addition, strain X1 was highly sensitive to cefoperazone and cravit, and intermediately sensitive to ten kinds of antibiotics including tobramycin, norfloxacin, sulperazone, kanamycin, gentamycin, fortum, vancomycin, neomycina, polymyxin B and lomefloxacin.