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.