Inhibition of Fish Pathogenic Aeromonas hydrophila and Edwardsiella tarda by Centella asiatica In-vitro

The present study assessed the in-vitro inhibition of fish pathogenic bacteria, viz., Aeromonas hydrophila and Edwardsiella tarda by aqueous, methanol and chloroform extracts of Centella asiatica by agar-disc diffusion, agar overlay well-diffusion, and broth dilution assays.The agar-disc diffusion assay with 10 μL of sterile crude C. asiatica extracts failed to inhibit A. hydrophila; while the crude chloroform extract inhibited E. tarda (11.25 ± 0.35 mm).In agar overlay well-diffusion assay, the methanol and chloroform extracts of C. asiatica (50 μL) inhibited E. tarda at varying levels exhibiting zones of 7.50 ± 0.70 mm and 30.50 ± 6.40 mm, respectively.With the increasing concentration of crude chloroform C. asiatica extract (0-10%/mL), an increased growth inhibition of E. tarda was noted in broth dilution assay.These results demonstrated that the chloroform extract of C. asiatica has the highest antibacterial activity against E. tarda in-vitro, which can be applied as an alternative to the commercial antibiotic to control E. tarda infection in aquaculture.