Isolation of Edwardsiella tarda from cultured hybrid snakehead (Channa maculata♀×C.argus♂) and its identification

Two pathogenic bacteria (ZS201364-1, ZS201364-2) isolated from diseased hybrid snakeheads (Channa maculata♀×C. argus♂) were identified to be Edwardsiella tarda by analyses of biochemical features and 16S rDNA sequence. The anaerobic, gram negative, bacilliform and motile isolates utilized glucoses and maltose as energy. Both indole and M.R. tests proved positive. The LD₅₀s of the isolates to healthy hybrid snakeheads were 7.1×10⁵ cfu · g^-1 and 5.6×10⁵ cfu · g^-1, respectively. The optimal growth conditions of strain ZS201364-1, which was highly susceptible to cefotaxime, ciprofloxacin and norfloxacin, were 25~35 ℃ pH 7~8 and 1% NaCl.