Antibacterial efficacy of Curvularia perotidis FN-OB51 endophyte against fish pathogens

Aims: Rapid bacterial infections in aquaculture drive farmers to use antibiotics, but overuse reduces their effectiveness, pollutes the environment, and harms consumers.To address this issue, this study investigates the antibacterial activities of the fungal endophyte Curvularia sp.FN-OB51, isolated from Ocimum basilicum leaves, and its potential against the fish pathogens Aeromonas hydrophila and Edwardsiella tarda. Methodology and results:The fungal endophyte Curvularia perotidis FN-OB51 was previously isolated from the leaves of O. basilicum plant.Based on the series of antibacterial studies that were carried out, the culture filtrate of Curvularia sp.FN-OB51 displayed antagonism against A. hydrophila and E. tarda owing to the existence of antibacterial compounds.Qualitative screening on the antibacterial activity was done using a disc diffusion assay.The fungal crude extract exhibited strong antibacterial activity on both bacteria, confirmed by the inhibition zone ranging from 15.5 0.5 to 23.0 1.0 mm.Following that, antibacterial activity was further quantitatively evaluated through broth microdilution assay.The MIC value for both test bacteria is 0.625 mg/mL.The MBC value for E. tarda is slightly higher, which was 1.250 mg/mL while MBC value for A. hydrophila remained at the MIC level.The destructive effect of crude extract was observed and confirmed by the scanning electron microscopy (SEM). Conclusion, significance and impact of study:In conclusion, the crude extract of C. perotidis FN-OB51 is a promising source of bioactive compounds with good antibacterial activity, particularly effective against fish pathogens.Therefore, crude extract can be developed into a potential prophylactic or therapeutic treatment for diseased fishes.