Effect of Streptomyces sp. RL8 on the survival of Artemia franciscana nauplii and resistance to Vibrio parahaemolyticus

Artemia franciscana nauplii were enriched with Streptomyces sp. RL8 in order to assess its effect on the survival rate of Artemia and its protective effects against Vibrio parahaemolyticus infection. Streptomyces sp. RL8 showed antagonistic activity against the opportunistic pathogenic Vibrio species of interest for aquaculture and decreased the growth of V. parahaemolyticus Collection of Aquatic Important Microorganisms (CAIM) 170 during in vitro co-culture experiments. Two experimental groups of nauplii, each replicated three times, were enriched with strain Streptomyces sp. RL8 at 10 6 and 10 8 colony-forming units (CFU)/ml; an unfed group served as the control. The experimental groups were challenged 24 h post-feeding with the strain V. parahaemolyticus CAIM 170 at 10 5 and 10 7 CFU/ml, and the survival of A. franciscana recorded at 24 and 48 h post-inoculation. Nauplii survival was significantly higher (88.75% and 86.25%) in the groups treated with Streptomyces sp. RL8 at 10 6 and 10 8 CFU/ml than in the control group (70.71%). These results confirm the probiotic properties of Streptomyces sp. RL8 and suggest that A. franciscana enriched with this strain can be fed to fish and shrimp larvae.