Virulence of Aeromonas hydrophila in Siamese fighting fish (Betta splendens) and the bacterium susceptibility to some herbal plants

Aeromonas hydrophila was isolated from diseased Siamese fighting fish Betta splendens Regans.  The virulence of A. hydrophiala to Siamese fighting fish was conducted by intraperitoneal injection of two doses of bacterial suspensions with 7.5×107 and 7.5×105 cfu per 0.05 ml. The cumulative mortality was observed in high and low dose groups which showed 98.33 and 20 percent, respectively. Moreover, five medicinal plants extracts namely Centella asiatica, Morinda citrifolia, Melissa officinalis, Piper sarmentosum and Terminalia catappa were determined for antimicrobial activities by broth dilution method. Terminalia catappa extract showed highest antimicrobial effect of MIC and MBC (25 and 12.5 mg mL-1), followed by M. officinalis and P. sarmentosum with the same values of MIC and MBC (12.5 and 25 mg mL-1).  Finally, Centella asiatica and Morinda citrifolia were similarly MIC and MBC (50 and 100 mg mL-1).  It was concluded that five medicinal plants can use to inhibit and kill A. hydrophila in fish.