致急性肝胰腺坏死病欧文氏弧菌的鉴定与分析OA

Shrimp farming industry has been severely threatened by acute hepatopancreatic necrosis disease(AHPND)that is one of shrimp diseases.In order to thoroughly investigate the pathogenic characteristics of the disease,preliminary pathogen screening and isolation identification were conducted using fluorescent PCR assay based on a batch of shrimp larvae suspected of AHPND,followed by gene sequencing,phylogenetic analysis and pathogenicity testing targeting the isolated strain.The results showed that the shrimp larvae were co-infected with AHPND-causing bacteria and Enterocytozoon hepatopenaei(EHP);yellow colonies were produced in TCBS medium by the isolated strain,and identified as non-Vibrio parahaemolyticus,all its tested genes including PirA,PirB,AP3 and AP4 were positive;and it was found that,by phylogenetic analysis of 16S rRNA,the isolated strain clustered with Vibrio owensii.Gene sequencing showed that complete pirA and pirB toxin genes were contained in the PVA1 plasmid of the isolated strain.Pathogenicity testing revealed that,when SPF Litopenaeus vannamei were immersed in a 106 CFU/mL solution of the isolated strain,typical AHPND symptoms appeared in their hepatopancreas,with a cumulative mortality rate approaching 60％within 48 hours post-infection,while that of VPAHPND control group was 100％.In conclusion,AHPND could also be caused by non-Vibrio owensii where corresponding virulence genes were carried,though its virulence differed from that of VPAHPND.Future researches on shrimp pathogen diversity and pathogenicity,as well as the efforts for disease control were supported by the data obtained in this study.