Time-kill kinetics and antimicrobial activities of Thai medical plant extracts against fish pathogenic bacteria

The main objective of this work was to conduct the microbial control of Thai herbs against fish pathogens and their time-kill kinetics activity. Ten medicinal plants were selected to test antimicrobial activity against aquatic pathogens including Aeromonas hydrophila, Flavobacterium sp., and Streptomyces sp. Caesalpinia sappan and Alpinia galangal extracts showed the best activity against A. hydrophila and Streptomyces sp. Among them, Caesalpinia sappan expressed the great activity against A. hydrophila and Streptomyces sp. with the test concentration of MIC values of 1.25 and 2.50 mg/mL and MBC values of 5.0 and 10.0 mg/mL, while the MIC and MBC values of A. galangal were found to be 2.50 and 10.0 mg/mL with Streptomyces sp. The plant extracts of C. sappan and A. galangal at 1MIC, 2MIC, and 3MIC values really showed time-kill kinetics potential against fish pathogen on period of 3-18 h. In conclusion, plant extracts are good potentials sources as antifish pathogens and safety in an aquatic ecosystem.