Traditional Indian herbal extracts used in vitroagainstgrowthofthepathogenicbacteria–Aeromonashydrophila

Crude ethanol extracts of Acalypha indica, Acorus calamus, Coleus aromaticus, Heliotropium indicum, and Indigofera aspalathoides were screened for antibacterial activity in vitro against the growth of the fish pathogenic bacteria, Aeromonas hydrophila. Terramycin, widely used to con- trol A. hydrophila in aquaculture, was used as a positive control. The herbs A. calamus and I. aspalathoides warded off the growth of the pathogen completely at minimum inhibitory concen- trations of 1.29 and 2.16 mg/l, respectively. A minimum bacterial concentration of 1.00 cfu occurred at concentrations of 0.77 mg/ml for A. calamus and 1.29 mg/ml for I. aspalathoides. The order of potency of the herbs in warding off growth of A. hydrophila in vitro was ranked: A. calamus, I. aspalathoides, C. aromaticus, A. indica, and H. indicum. The inhibitory potency of A. calamus and I. aspalathoides was significantly higher (p<0.05) than that of the positive control, indicating the potential of these herbs to replace antibiotics in controlling A. hydrophila infection.