Efficacy of bauhinia sirindhorniae on resistance to against streptococcus agalactiae in Nile tilapia (Oreochromis niloticus)

Abstract

The studies on antibacterial activity of crude extract from Bauhinia sirindhorniae against Streptococcus agalactiae were conducted by using leaves and flowers of B. sirindhorniae extracted by acetone and ethanol 95%. Antibacterial activity, performed by disc-diffusion method, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) for B. sirindhorniae extracts were determined by broth dilution method. The results revealed that the highest activity against S. agalactiae was found in leaves extract using of ethanol 95% with inhibition zone of 15.53+0.65 mm and the MIC value against S. agalactiae was 1,562.5 mg/l. The determination of MBC was not observed in any concentration of B. sirindhorniae extracts. Additionally, supplementation of leaves extract of B.sirindhorniae in Nile tilapia (Oreochromis niloticus) diet was also conducted to investigate the effect on resistance to S. agalactiae. The results showed that weight gain and specific growth rate were not significantly difference (P>0.05). Fish fed with 1% extract had significantly lowest mortality (P<0.05) and had highest relative percentage survival (RPS).