Antibacterial activities of some Borneo plant extracts against pathogenic bacteria of Aeromonas hydrophila and Pseudomonas sp

The objective of the present study was to explore the antibacterial activity from some plant extracts against Aeromonas hydrophilla and Pseudomonas sp. pathogenic bacteria for tilapia (Oreochromis niloticus). The plant extracts were obtained by using ethanol and the concentration of the extract was 500-600 mg L-1 and the the inhibition zone was measured after 24 h at 30°C. The results showed that 16 extracts have antibacterial activity with more than 10 mm against A. hydrophila and eight extracts against Pseudomonas sp. The highest activity was shown by the black cumin (Nigella sativa) extract against both bacteria. The effective dose of the extract as an antibacterial substance, against both bacteria, were 800 and 900 mg L-1 Boesenbergia pandurata to A. hydrophila, 600 and 900 mg L-1 Solanum ferox to Pseudomonas sp., and concentration of Zingiber zerumbet 200 and 2,000 mg L-1 effective to inhibit A. hydrophila bacteria.