In Vitro Inhibitory Activity of the Leaf Methanol Extract of Green Tea (<i>Camellia sinensis</i>) against <i>Lactococcus garvieae</i> and <i>Aeromonas hydrophila</i> Isolated of Rainbow Trout (<i>Oncorhynchus mykiss</i>)

Abstract

Camellia sinensis Linn is a well-known medical herb that grows in various parts of the world. In the current study, the antimicrobial activity of methanol extract from C. sinensis leaves against Lactococcus garvieae and Aeromanas hydrophila isolated from rainbow trout ( Oncorhynchus mykiss ) was investigated. The growth inhibitory effects of green tea extract was determined by disc diffusion method (3 times on different days), minimum inhibitory concentration (MIC) using serial dilution and minimum bactericidal concentration (MBC). For the L. garvieae and A. hydrophila , the zone diameter inhibition (ZDI) of extract ranged 2.30 - 16.5 mm. The highest ZDI (16.50 ± 1.12 mm) for L. garvieae was observed at 100 mg &bull; ml - 1 and for A. hydrophila (16.20 ± 0.95 mm) at 250 mg &bull; ml - 1 concentration of green tea extract (P < 0.05). At 20, 30, 40 and 100 mg &bull; ml - 1 concentrations of extract, ZDI values of A. hydrophila and L. garvieae showed significant difference (P < 0.05). The lowest MIC value for the extract was 0.8 mg &bull; ml - 1 against both L. garvieae and A. hydrophila . From the results of the present study, it can be concluded that methanol extract of C. sinenses leaves could be effective for the inhibition of A. hydrophila and L. garvieae in rainbow trout.