Triagem de genes PirVP em bactérias do gênero vibrio isolados de estuários com atividade de carcinicultura no estado do Ceará

Abstract

Shrimp farming is a branch of aquaculture that is growing every year, thus demanding ever greater productions of the Pacific white shrimp, Litopenaeus vannamei. Due to the densification of crops, sharing of water and highly eutrophic effluents, shrimp production suffers from some bacterial diseases, including Acute Hepatopancreatic Necrosis Syndrome, mainly caused by Vibrio parahaemolitycus. The present research aimed to verify the presence of pathogenic bacteria belonging to the Vibrio genus that have genes capable of expressing toxins causing the Acute Hepatopancreatic Necrosis Disease (AHPND) in three estuaries of the State of Ceará that are centers for the production of marine shrimp in captivity (Pirangi, Jaguaribe and Acaraú). In each estuary, two collections were carried out. Thus, six sub-samples were processed, originating from two environmental matrices, water and sediment. From these samples, strains with a biochemical profile compatible with the Vibrio genus were isolated. The count of Vibrio colonies in the samples was performed. After isolation and purification of the colonies, total DNA extraction was performed to verify the presence of bacteria belonging to the genus Vibrio and species V. parahaemolyticus using the Polymerase Chain Reaction (PCR) method. A total of 109 strains were subjected to tests in order to detect genes related to the production of the toxin that causes AHPND. Eleven strains were positive in at least one of the seven methods described by the OIE. However, it was not possible to identify the genes capable of encoding PirA and PirB toxins. Only one strain was considered suspect because it presented a positive result for the method that identifies V. parahaemolyticus carrying AHPND (VpAHPND). None of these 11 strains belong to the species V. parahaemolyticus. From the results obtained, it is possible to state that the plasmid that carries the toxin genes capable of causing AHPND is already circulating in estuaries with the presence of shrimp farming activity in Ceará.