Efficacy of Thai traditional herb extracts against fish and shrimp pathogenic bacteria

Sixteen species of Thai traditional herbs were selected for this study. They were Andrographis paniculata, Cassia alata, Clinacanthus nutans, Eclipta alba, Momordica charantia, Phyllanthus acidus, P. amarus, P. debilis, P. pulcher, P. reticulatus, P. urinaria, Psidium guajava, Tinospora cordifolia, T. crispa and white and red strains of Ocimum sanctum. Using an agar plate dilution method, they were tested for antibacterial activity against the pathogenic bacteria: Aeromonas hydrophila, a Streptococcus species and 10 strains of Vibrio. Eleven of the tested herbs showed antibacterial activity. Among them, P. guajava and M. charantia displayed the highest activity against Vibrio harveyi and V. parahaemolyticus. The minimal inhibitory concentration (MIC) of P. guajava against the tested bacteria was found to be 0.625 mg/ml, while the MIC of M. charantia was 1.25 mg/ml.