Screening and selection of bacteria inhibiting white spot syndrome virus infection to Litopenaeus vannamei

A total of 173 bacterial strains were isolated from different sources at different regions such as fermented foods, shrimp guts, sea water, mangrove water, and sediments. These bacteria were screened against white spot syndrome virus (WSSV) infection in Palaemon paucidens. Based on mortality, white spot level, and healthiness, three bacterial strains were selected and identified using 16S rRNA gene sequencing. These bacterial strains were Bacillus subtilis KA1, B. licheniformis KA2, and B. subtilis KA3. WSSV challenge test in pilot scale was conducted using Litopenaeus vannamei with B. subtilis KA1 and B. subtilis KA3. The survival ratio of shrimp was 0% for WSSV control after 17th days, 84% for B. subtilis KA1 plus WSSV after 26th days, and 28% for B. subtilis KA3 with WSSV after 26th days. B. subtilis KA1 showed good growth at 18–37 °C in with and without 3% NaCl, and therefore can be applied to aquaculture at low to high temperatures. B. subtilis KA1 produced protease and lipase which can increase digestion to shrimp; exhibited antibacterial activity against Vibrio parahaemolyticus; and significantly increased the survival of WSSV challenged shrimps.