Treatment with native strains of Bacillus spp, produces a similar effect as oxytetracycline on the survival of Litopenaeus vannamei shrimp infected with Vibrio parahaemolyticus

The aim of this study was to compare the survival of Litopenaeus vannamei shrimp infected with two strains of Vibrio parahaemolyticus (strains 25 and Lang 60) after being treated with two strains of Bacillus: B. amyloliquefaciens 37B and B. licheniformis 53IB, as well as oxytetracycline (control). Shrimp were collected from a shrimp farm in Tumbes, Peru, and from the mangrove swamp of Puerto Pizarro, Tumbes. Eight strains of Vibrio spp. and 26 strains of Bacillus spp. were isolated from them, and nine Bacillus strains were selected from the latter for in vitro inhibition against the eight Vibrio strains. The Bacillus strains were cultured in liquid medium, and the supernatant containing the antibacterial substances secreted by Bacillus was separated. Two Bacillus strains (37B and 53IB) that produced the greatest in vitro inhibition were selected to challenge strains 25 and Lang 60 (V. parahaemolyticus) in in vivo experiments. Most Bacillus strains inhibited Vibrio in vitro; eight of them, including 37B and 53IB, did so to a greater extent. Furthermore, strains 37B and 53IB inhibited the growth of strains 25 and Lang 60 in the hepatopancreas of shrimp in vivo, achieving survival rates similar to those obtained with oxytetracycline. It is concluded that native strains 37B (B. amyloliquefaciens) and 53IB (B. licheniformis) can control Vibrio parahaemolyticus infection to the same extent as oxytetracycline, constituting an alternative to antibiotic treatment in shrimp culture.