Evaluation on Antimicrobial Activity of Extract Controlling the Growth of Gram-Positive Bacteria.

This study investigated bacterial growth-inhibitory effect of 69 therapeutic herbal plants extracts on 9 bacterial strains using a disc diffusion assay. Especially, the antimicrobial activity of , which showed different activity on pathogenic Gram-positive and Gram-negative bacteria, was evaluated by MIC (minimal inhibition concentration) and biofilm formation assay. The effect of extract on bacterial cell membranes was examined by measurement of protein leakage (optical density at 280 nm) and scanning electron microscope (SEM). No clear zone was formed on discs containing Gram-negative bacteria, but Gram-positive bacteria exhibited clear zones. The MICs of extract were 8 μg/mL for , and 16 μg/mL for Enterococci and . In addition, biofilm formation was inhibited at concentration 8-16 μg/mL. Protein leakage values and SEM images revealed that cell membranes of Gram-positive bacteria were impaired following exposure to the extract. Further, the extract inhibited the growth of in sausages. These results indicate that extract could be utilized as a natural antimicrobial agent against Gram-positive bacteria.