Abstract:

To identify the mortality cause of Macrobrachium rosenbergii, the strain with growth advantage was isolated from the dying M. rosenbergii, and its hemolysis, gram staining, morphological characteristics, physiology and biochemistry were determined. The results showed that, the isolated strain was a gram-negative while oxidase, l-arabinose, glucose (acid), peptone water, arginine dihydrolase, gelatin, and phenylalanine were positive. The 16S rRNA gene of this isolate was sequenced and the phylogenetic tree was constructed. The isolated strain was clustered with Aeromonas caviae and had a close genetic relationship. The isolated strain was confirmed as Aeromonas caviae (Accession number MN736843) based on its biochemical characters and 16S rRNA sequence analysis. The artificial infection experiment with the injection method confirmed that the isolated strain was highly pathogenetic to M. rosenbergii. The results of drug susceptibility tests revealed that the strain was highly sensitive to ceftriaxone, chloramphenicol, florfenicol, tetracycline and doxycycline; it was moderately sensitivity to kanamycin and resistant to ciprofloxacin, norfloxacin, erythromycin, azithromycin, novobiocin, streptomycin, compound sulfamethoxazole and rifampicin. This study provides a reference and theoretical basis for the pathogen identification, drug diagnosis and treatment of Aeromonas cavia in M. rosenbergii.

Key words: Macrobrachium rosenbergii, Aeromonas caviae, isolation and identification, gram staining, biochemical identification, drug sensitivity test