Sensitivity of Fish Pathogenic Bacteria to Various Medicinal Herbs

The sensitivity of certain local medicinal herbs was evaluated against pathogenic Aeromonas hydrophila, Pseudomonas fluorescens and Edwardsiella tarda bacteria of fish during the period from April 2001 to March 2002. A suspension of freshly cultured experimental bacteria (2 x 107 CFU / ml) was prepared and 0.1 ml of this suspension was spread over the tryptic soya agar (TSA) plates. Then crude extract (0.1ml / plate) of each herb was inoculated in the middle of the cultured plate to detect the response. The herbal extract was categorized as high, medium and low inhibitory responded by observing the clear zone of inhibition. Fine extract of the high inhibitory responded herbs was applied under in vitro conditions against the bacteria tested. Twenty-one (80.76%), twenty-four (92.30%) and twelve (46.15%) species of the herbs tested showed antibacterial effect against A. hydrophila, P. fluorescens and E. tarda, respectively. Among them, high inhibitory responded herbs were 38.09% for inhibition of A. hydrophila and P. fluorescens and 38.33% for E. tarda. However, the extract collected from bulb of Allium sativum for inhibition of A. hydrophila and P. fluorescens and the decoction obtained from leaves of Calotropis gigantea for E. tarda were detected to be the most promising herbs considering effectiveness with minimal inhibitory concentration (MIC) among all of the herbs tested. Key words: Sensitivity; pathogenic bacteria; herbal extract; minimal inhibitory concentration doi: 10.3329/bjvm.v2i1.1941 Bangl. J. Vet. Med. (2004). 2 (1) : 75-82