Traditional Indian Herbal Extracts Used in Vitro against Growth of the Pathogenic Bacteria – Aeromonas Hydrophila

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 control 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 concentrations 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. Introduction Aeromonas hydrophila is a ubiquitous gramnegative bacterium in the aquatic environment that affects both cultured and feral fisheries, inflicting severe economic losses. As a primary pathogen, it causes severe ulcerative dermatitis leading to motile aeromonad septicemia (Hayes, 2000) and, as a secondary pathogen, it is implicated in the devastating epizootic ulcerative syndrome (Thampuran et al., 1995). Chemicals such as malachite green, formalin, sodium chloride, sulphonomide, nitro* Corresponding author. Tel.: +91-431-2407045, +91-431-2407040, e-mail: [email protected]