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In this paper, the pathogenic Aeromonas isolated from diseased farmed eels (Anguillajaponica and Anguilla rostrata) were identified by physiological and biochemical methods.Some bacteria were used to challenge eels to determine pathogenic isolates. Pathogens classifiedto the genus of Aeromonas were identified by the Biolog Automic Identification System andgene sequencing analysis. The sensitivity of32pathogens belonging to the genus Aeromonas to30drugs was also tested. The main results are as following:1. Totally56strains of bacteria were isolated from liver and kidneys of diseased farmed eelsof9batches. Five isolates were used to challenge eels after primary biochemical identification.The result showed that3isolates were eel’s pathogens, including3species of Aeromonasbestiarum, Aeromonas popoffii and Aeromonas allosaccharophila after primary indentificated bybiochemical kit.2. Five newly isolated and twenty-seven saved pathogens belonging to the genusAeromonas were classified and identified by the Biolog Microbial Identification System. Theresults showed that the32pathogens were identified as A. hydrophila (21), A. veronii (7), A.caviae (1), A. jandaei (2) and A. bestiarum (1). The similarity rate of25pathogens was morethan80%, while the rate of7pathogens was low, including2isolates of Aeromonas hydrophila,3isolates of Aeromonas veronii,1isolate of Aeromonas jandaei and1strain of A. bestiarum.3. These Thirty-two strains of pathogenic Aeromonas were also identified by16S rRNA,cpn60, rpoB, gyrB and dnaJ gene sequencing analysis, the results showed that32pathogenswere classified into4populations: A. hydrophila (21), A. veronii (7), A. caviae (2) and A. jandaei(2). Moreover, the average genetic distances of gene cpn60and dnaJ between differentpathogenic Aeromonas were higher than the other gene sequences, with0.082and0.089,respectively. Therefore, the gene cpn60and dnaJ could be considered as an important basis formolecular identification in the genus Aeromonas.4. The sensitivities of32pathogenic Aeromonas to12kinds (including30drugs) weretested in this study. The results indicated that all pathogens were sensitive to3drugs of amikacin,gentamicin and ceftazidime, more than80%of32strains were sensitive to16drugs, includingcefuroxime, cefotaxime, nitrofurantoin, kanamycin, lomefloxacin, azithromycin, streptomycin,levofloxacin, norfloxacin, ceftriaxone, spectinomycin, doxycycline, piperacillin, augmentin,nalidixic acid and tetracycline. While11drugs of novobiocin, cefaclor, cephradine, cefazolin, cephalothin, rifampicin, sulfamethoxazole, ampicillin, acetylspiramycin, carbenicillin andpenicillin were resistant.5. In conclusion,32pathogenic Aeromonas isolated from diseased farmed eels wereidentified by the Biolog Microbial Identification System and gene sequencing analysis. Theresults of Biolog system were consistent with the results of gene sequencing analysis. The32pathogens were identified as A. hydrophila, A. veronii, A. caviae and A. jandaei. In which, the A.hydrophila and A. veronii were major species of pathogens belonging to genus Aromonas, andthe A. jandaei was improved to be a pathogen of farmed eels in the first time.
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