Abstract
An in vitro assessment of antimicrobial properties of aqueous and ethanol extracts from solo garlic (Allium sativum), garlic chive (Allium tuberosum) and betel leaves (Piper betle) on six bacterial pathogens in aquaculture, and a challenge of Nile tilapia, Oreochromis niloticus with Streptococcus agalactiae were performed. Generally, minimum inhibitory concentrations (MIC) ranged from 26.63 to 53.25 mg mL(-1) for aqueous solo garlic (G) and 14.60 to 29.20 mg mL(-1) for garlic chive extracts for all pathogens tested. Ethanol extract of betel leaves (P) exhibited the strongest antibacterial activity (0.15-0.60 mg mL(-1)). P and G incorporated in feed at high and low doses as multiples of MIC [High; H (10X for PH and 3X for GH) and Low; L (3X for PL and 1X for GL)] were fed to tilapia followed by in vivo challenge against S. agalactiae (1 x 108 CFU mL(-1)). Ethanol extract of P. betle significantly improved survival (P<0.05; PH= 100%, PL = 77%). White blood cells (WBC), lymphocytes and monocytes differed significantly (P<0.05) among treatments and the highest WBC value (1.175 x 10(3)) was for PH. Use of ethanol extract of Piper betle seems promising for sustainable disease management in aquaculture.
