ANTIBACTERIAL POTENTIAL OF LOCALLY AVAILABLE AQUATIC AND TRADITIONAL MEDICINAL PLANTS AGAINST AQUACULTURE BACTERIAL PATHOGENS

Aquaculture is the one of the fastest growing food-producing sectors in the world. However, occurrence of outbreaks of bacterial diseases obstructs its further development. Antibiotics and probiotics are the common methods used to treat and control bacterial diseases. Nevertheless both methods give rise to concern such as development of antibiotic resistance bacteria and accumulation of antibiotic residues in the fish and environment. Thus, search of new antibacterial substances that are not persistent in the environment for a long period of time is very much needed. The objective of the present study was to test antibacterial activity from extracts of four traditional medicinal plants against aquaculture bacterial pathogens including Aeromonas hyrdophilla, Aeromonas salmonicida, Aeromonas caviae, Vibrio harveyi, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio anguillarum, using well diffusion method. Water, ethanol, chloroform and hexane were used as solvents to extract the plants samples. Inhibition zone of bacterial growth by the plant extracts at concentration of 10 milligram per millilitre was measured after 24 hour at 28⁰C. Of the four plants, Artemisa sp (mugwort) and Cassia alata (candle bush) displayed good antimicrobial activities based on the size of inhibition zone and number of bacteria inhibited. Artemis sp was able to inhibit all Vibrio species tested and Cassia alata was able to inhibit all the test bacteria. From the phytochemical analysis, it suggests that all the four plants were found to contain alkaloids, tannins, saponins, flavonoids and phenols. These may explain the antimicrobial activities exhibited by the plants. Although the plants may contain substances with antibacterial activities, their usefulness to aquaculture is limited until their non-toxicity to fish is proven.

Keywords: plant extract; antimicrobial activity; aquaculture bacterial pathogens