ISOLATION, IDENTIFICATION AND PATHOHISTOLOGICAL OBSERVATION OF AEROMONAS VERONII FROM PROCAMBARUS CLARKII

To identify the aetiology of the outbreak of the disease in cultured Procambarus clarkii, we isolated a dominant strain of bacteria (QD160502) from the hepatopancreas of diseased Procambarus clarkii. It was identified as Aeromonas veronii based on morphological observation, biochemical identification, physiology characteristics and sequencing of 16S rDNA and gyrase B subunit gene. The symptoms of P. clarkii artificially infected with strain QD160502 were similar with those of natural infected P. clarkii. The pathological changes were observed by HE staining. The histological changes of P. clarkii caused by A. veronii infection were gradually aggravated. 12 hours after challenge, some transferred vacuoles containing granular materials were found in hepatopancreas blasenzenllen cells. 24 hours after challenge, inflammatory cells infiltration was observed in hepatopancreas, and intestinal connective tissue atrophy and vacuole-like dilations were observed in myocardial tissue. 48 hours after challenge, mass of hepatopancreas restzellen cells and blasenzenllen cells disintegration, intestinal mussel flods decreased and vacuole-like dilations increased in the myocardial tissue. 72 hours after challenge, hepatopancreas and intestinal epithelial cells became necrotic and damaged, and hyaline blood cells aggregation were observed in myocardial tissue. The antimicrobial sensitivity test showed that the strain QD160502 was highly sensitive to enrofloxacin, norfloxacin, tetracycline, doxycycline, etc, but resistant to penicillin, streptomycin, kanamycin, etc. This study provides theoretical basis for the prevention and treatment of A. veronii infection diseases in P. clarkii.