Ethanol Extract of Ulmus pumila Root Bark Inhibits Clinically Isolated Antibiotic-Resistant Bacteria

In this study, root bark of Ulmus pumila (U. pumila) was extracted with ethanol, and then the antimicrobial effects were tested on clinically isolated 12 MRSA strains and 1 standard MRSA strain. U. pumila showed antibacterial activities against all MRSA strains. Minimum inhibitory concentration (MIC) of U. pumila root bark against all MRSA strains revealed a range from 125 to 250  μ g/mL. These results may provide the scientific basis on which U. pumila root bark has traditionally been used against infectious diseases in Korea. In real-time PCR analysis, the sub-MIC (64-125  μ g/mL) concentrations of U. pumila root bark extract showed the inhibition of the genetic expressions of virulence factors such as mecA, sea, agrA, and sarA in standard MRSA. Phytochemical analyses of U. pumila root bark showed relatively strong presence of phenolics, steroids, and terpenoids. These results suggest that the ethanol extract of U. pumila root bark may have antibacterial activity against MRSA, which may be related to the phytochemicals such as phenolics, steroids, and terpenoids. Further studies are needed to determine the active constituents of U. pumila root bark responsible for such biomolecular activities.