In vitro inhibition of Saprolegnia by bacteria isolated from lesions of salmonids with saprolegniasis

Abstract

A study was conducted to investigate the antifungal activity of some bacteria isolated from the lesions of salmonid fishes with saprolegniasis. Five of 47 isolates inhibited the growth of Saprolegnia parasitica H2 and S. salmonis NJM 9851 on solid media. Among 8 media examined, BHI, HI, and to a lesser extent NA were suitable for demonstrating the antifungal activity. The inhibitory activity against the tested Saprolegnia did not reside in supernatant of bacterial broth culture of the selected strains. The strains which produce antifungal substances belong to the genera Alteromonas, Pseudomonas, and Aeromonas. These results suggest that the selected bacteria are natural competitors of Saprolegia, and may be used for biocontrol of Saprolegnia in aquaculture.