##plugins.themes.huaf_theme.article.main##
Abstract
This study was conducted to investigate the growth-inhibiting effect towards Streptococcus agalactiae isolated from infected tilapia (Oreochromis spp.) by herbal extracts, namely cinnamon (Cinnamomum verum), ginger (Zingiber cassumunar), king of bitters (Andrographis paniculata), fish mint (Houttuynia cordata), and perilla leaf (Perilla frutescens). The extracts of these herbs were prepared in ethanol 96% or methanol 99.8%, which were subsequently subjected to heat treatment and vacuum evaporation to remove the solvents. The final concentration of the herbal extracts was 2000 mg/ml. The results showed that, cinnamon extract in either ethanol 96% or methanol 99.8% exhibited the strongest growth-inhibiting effect towards Streptococcus agalactiae SA3 and SA4 isolates, with the diameters of inhibition zones 17.67 mm and 16.25 mm, 33.42 mm and 32.75 mm, respectively. Whereas ginger and king of bitters extracts showed a medium inhibition (diameters of inhibition zones were in the range of 9.50 – 13.08 mm), fish mint and perilla leaf showed a weak inhibition (diameters of inhibition zones were in the range of 2.92 – 7.42 mm). The MBC (minimal bactericidal concentration) and MIC (minimal inhibitory concentration) values of cinnamon extracts were 16,000 μg/ml and 8,000 μg/ml for SA3 isolate, respectively; and 8,000 μg/ml and 4,000 μg/ml for SA4 isolate, respectively. Cinnamon extract in ethanol 96% or methanol 99.8% can be considered as a potential herbal extract for prevention of disease caused by Streptococcus agalactiae in tilapia.
Keywords: antagonism, herbal extracts, Oreochromis spp., Streptococcus agalactiae