The potential of bangkal leaf (Nauclea subdita [korth.] steud.) extract as antibacterial in catfish pangasius hypophthalmus culture

This study was aimed to evaluate the ability of bangkal leaf extract (Nauclea subdita [Korth.] Steud) as an antibacterial against Aeromonas hydrophila in Pangasius hypophthalmus (in vitro and in vivo). Bangkal leaves were extracted in methanol, ethyl acetate, and n-hexane as solvents. The extracts were assayed for coculture with A. hydrophila. The best fraction of the coculture assay was evaluated for minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and Scanning Electron Microscope (SEM). In vivo assay evaluated the survival rate of infected fish after administration of extracts and A. hydrophila colonies into the fish blood. The coculture assay showed that ethyl acetate fraction had the best ability to kill A. hydrophila. MIC assay of ethyl acetate fraction could inhibit at the minimum dose of 25 mg L^-1. MBC assay showed that A. hydrophila could not grow at 50 mg L^-1 (2xMIC). Moreover, SEM analysis showed damage to A. hydrophila bacterial cells after administration of N. subdita ethyl acetate fraction of 500 mg L^-1. Survival rate appeared at the dose of 100 mg L^-1, in which the catfish mortality did not occur. The observation of bacterial colonies in the catfish blood showed no bacterial growth under the extract treatment of 100 and 150 mg L^-1. Therefore, ethyl acetate fraction of 100 mg L^-1 was recommended to overcome infections caused by A. hydrophila.