Subinhibitory Concentrations Of Chinese Herbal Medicine Fructus Forsythia Extract Inhibits Staphylococcus Aureus Alpha-hemolysin Secretion Activity

Staphylococcus aureus is a kind of frequent pathogenic bacterium, that cancause mastitis, traumatic infection and many other varieties of zoonosis. With theabuse of antibiotics, more and more drug-resistant strains were found.Thepathogenicity of staphylococcus aureus is closely related to a variety of virulencefactors. As one of its most important virulence factors，alpha-hemolysin plays a keyrole in the pathogenicity and avoiding the body process. People now keep tringy tofind drugs with new mechanisms that can reduce the virulence of virulence factorsespecially the alpha–hemolysin.Fructus forsythia is commonly heat-clearing and detoxicating drug, which canreducing swelling, dispelling wind and heat from the body in traditional Chinesemedicine. Fructus forsythia has extensive pharmacological action such as antibacterial,antiviral, antipyretic anti-inflammatory and so on.Ethanol reflux method was used to obtain the extracts from fructus forsythia.MIC determination，hemolysin assays, western blotting，real-time RT-PCR，Live/deadcell staining and lactate dehydrogenase (LDH) assays were performed to investigatethe impact of fructus forsythia extracts on the α-hemolysin production ofStaphylococcus aureus. The MICs of the extracts from fructus forsythia against S.aureus strains were all>2048μg/ml, which indicate that the extracts from fructusforsythia have little influence on S.aureus growth. When the drug concentration was16-128μg/ml S. aureus α-hemolysin production was remarkably decreased in adose-dependent manner. The data indicate that these extracts could potentially beuseful in developing drugs that are aimed at staphylococcal α-hemolysin.