Efeito do uso de bactérias probióticas na sobrevivência de larvas de Litopenaeus vannamei expostas à infecção experimental por Vibrio spp

Abstract

This study aimed to evaluate the survival of Litopenaeus vannamei shrimp larvae treated with probiotic bacteria and subsequently infected by Vibrio harveyi and Vibrio alginolyticus. Shrimp were kept in two 80L tanks under similar culture conditions, but only one tank was previously treated with commercial probiotic (Bacillus spp.) added daily in the water at a concentration of 105 CFU/ml. This protocol was maintained until the animals reach the stage of development needed for the infection experiments by Vibrio spp. Three independent infection experiments were performed: Zoea1 to Zoea3, Mysis1 to Mysis3 and Postlarvae (PL)10 to PL14 with the following treatments with four replicates each: only V. harveyi; commercial probiotic + V. harveyi; only V. alginolyticus; commercial probiotic + V. alginolyticus; and without Vibrio spp. and probiotic (Control). In the experiment with PL, only the treatments with V. harveyi; commercial probiotic + V. harveyi and control were used. Vibrio species were inoculated only at the beginning of each experiment at a concentration of 107 CFU/ml. At the end of experiments, a sample of water and shrimp from each experimental unit was submitted to quantification of Vibrio spp. Additionally, was realized an antagonism test of Bacillus spp. against Vibrio spp. In the experiments with zoea and mysis, larvae cultured in treatment V. harveyi had a significantly lower survival when compared with treatments V. alginolyticus and control. There was a significant increase in survival of zoea and mysis larvae treated with probiotic + V. harveyi with 81.07 and 90.13%, differentiating the larvae infected only with V. harveyi with 12.80 and 69.13%, respectively. There were no significant differences in survival of postlarvae among treatments. Total Vibrio spp. counts decreased in the water and shrimp of treatments with the use of probiotic. The probiotic (Bacillus spp.) showed inhibitory activity against Vibrio spp. in vitro. The results indicated an increase in the survival of early larval stages (zoea and mysis) infected by V. harveyi after treatment with Bacillus spp. The administration of probiotic bacteria is a promising alternative for the prevention of Vibrio spp. in larviculture of L. vannamei.