Aquaculture nursery systems after infection with Vibrio harveyi

Abstract

Present study evaluated the survival, post-larvae quality, and the population of Penaeus monodon (Black tiger shrimp) and Oreochromis niloticus (Tilapia), after the addition of two strains of bacteria i.e Lactobacillus sp. and Bacillus sp. The Vibrio harveyi were isolated and identified from hatchery-reared larvae, at Biotechnology Research Department Ministry of Education, Republic of Union of Myanmar. Preliminary screening for antimicrobial activity of six Lactobacillus sp. and six Bacillus sp. Incubated and tested with V. harveyi using agar, well diffusion assay and tube screening methods. Inhibition activity results were the best at 3 days incubation for Lactobacillus sp. and the optimal result for inhibition activity for Bacillus megaterium at 5 days, with lactose sugar on V. harveyi. Before in vivo test, in vitro inhibition test of V. harveyi competition with probiotic of different concentrations of 10 ml/ton, 20 ml/ton, 30 ml/ton and 40 ml/ton. The results in all probiotic treatments were almost similar. Inhibitory affects were found in tube screening method, where, V. harveyi level reduced to 10 3 CFU/ml from 10 7 CFU/mlin 4 days. The pathogenicity test was conducted for a period of 2 days with Penaeus monodon (Black tiger shrimp) at post larval stages and Oreochromis niloticus (Tilapia) at fingerling stages, where they were exposed for 106, 107 and 108 CFU/ml of V. harveyi resulted 100% mortality. The probiotic treatment exhibited 50%, 70% and 80% survival rate of the fish infected with 106, 107 and 108 CFU/ml, respectively. It was detected the lower load of Vibrio ssp. bacteria with potential of pathogenicity after feeding with six Lactobacillus sp. and six Bacillus sp.