Molecular Epidemiological Investigation Of Aeromonas Veronii From Channel Catfish In Sichuan District

Aeromonas veronii(A.veronii) is a kind of opportunistic pathogenic bacteria and can be commonly found in sea water, fresh water and the natural environment. It can infect a large number of aquatic animals (e.g., loach, chinese flocking chela crab and brocade carp) and cause many different clinical symptoms, such as anal swelling, ascitic fluid, liver hemorrhage etc., which result in significant economic losses in the aquaculture industry and is seriously harmful to fishery development in China. At the same time, A.veronii can also infect human beings and cause suppurative arthritis, diarrhea and sepsis. At present the reports of research focused on the isolation and identification of A.veronii from channel catfish, but there was little information about epidemiological survey infected with A.veronii. Epidemiology, as a subject about disease distribution rules and influence factors, can could provide important reference material for exploration of the causes, control and prevention of disease. In this paper, we tried to study on the molecular epidemiological investigation of A. veronii from channel catfish in Sichuan district, and lay foundation for control and prevention of A.veronii.The natural disease of channel catfish from different areas in Sichuan district were gathered and identified through separation of bacteria cultivation and detection of biochemical and physiological characteristics. Simultaneously molecular identification of analysis of the nucleotide sequence of the16S rDNA gene was applied to determine the species of the isolated bacteria. Based on these, Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR) and Amplified Fragment Length Polymorphism (AFLP) were used to certain the genotype of the major epidemic disease strains on channel catfish in Sichuan district.According to the biological characteristics of bacteria, and combined with molecular identification of analysis of the nucleotide sequence of the16S rDNA gene, we isolated and identified the bacteria form channel catfish in Sichuan province, and reached a conclusion that there were25strains of A.veronii. Combined with another14strains A.veronii (one was bought from ATCC and the others were isolated from channel catfish), the application of ERIC-PCR on gene typing of these pathogenic A.veronii strains of aquatic animal pathogens was studied. ERIC-PCR pattern of39strains generated seven subgroups at the similarity of0.77,48.7%of the A.veronii belong to E I,7.4%belong to EⅡ,5.1%belong to EIII, and both of the EⅣ and EⅤ only have1strain, EⅥ contains4strains, EⅦ includes9strains. EⅠ was the dominant genotyping microorganisms of the pathogenic A.veronii among the channel catfish, and it distributed at Meisha、Deyang、 Mianyang、Jianyang and Chengdu. In addition, the A.veronii form different farms belong to different genetype, which is given priority to a gene type and cross a few other genetic type. AFLP pattern of39strains generated nine subgroups at the similarity of0.67, the fourth subgroup have14strains,17.9%belong to AⅤ. Whether the ERIC-PCR or AFLP in genotyping were30%, which explains that A.veronii have one gene type as the main popular type. Besides, the strains isolated from different areas not only contain different genetic composition, but also express diversity characteristics, in addition to the single gene type in few area.