pirAB vp -Bearing Vibrio parahaemolyticus and Vibrio campbellii Pathogens Isolated from the Same AHPND-Affected Pond Possess Highly Similar Pathogenic Plasmids

摘要

Acute hepatopancreatic necrosis disease (AHPND) is a severe shrimp disease originally shown to be caused by virulent strains of Vibrio parahaemolyticus (VP_(AHPND)). Rare cases of AHPND caused by Vibrio species other than V. parahaemolyticus were reported. We compared an AHPND-causing V. campbellii (VC_(AHPND)) and a VP_(AHPND)isolate from the same AHPND-affected pond. Both strains are positive for the virulence genes pirAB ~( vp ). Immersion challenge test with Litopenaeus vannamei indicated the two strains possessed similar pathogenicity. Complete genome comparison showed that the pirAB ~( vp )-bearing plasmids in the two strains were highly homologous, and they both shared high homologies with plasmid pVA1, the reported pirAB ~( vp )-bearing plasmid. Conjugation and DNA-uptake genes were found on the pVA1-type plasmids and the host chromosomes, respectively, which may facilitate the dissemination of pirAB ~( vp ). Novel variations likely driven by IS Val1 in the genetic contexts of the pirAB ~( vp )genes were found in the two strains. Moreover, the VC_(AHPND)isolate additionally contains multiple antibiotic resistance genes, which may bring difficulties to control its future outbreak. The dissemination of the pirAB ~( vp )in non- parahaemolyticus Vibrio also rises the concern of missing detection in industrial settings since the isolation method currently used mainly targeting V. parahaemolyticus . This study provides timely information for better understanding of the causes of AHPND and molecular epidemiology of pirAB ~( vp )and also appeals for precautions to encounter the dissemination of the hazardous genes.