Study on Sub-minimal Inhibitory Concentration of Tanreqing Injection in Inhibiting Hemolytic Activity of Staphylococcus aureus α-hemolysin / 中国实验方剂学杂志

ABSTRACT

Objective:To study whether Tanreqing injection （TRQ） can alleviate the body injury in the process of infection by inhibiting the production and release of <italic>α</italic>-hemolysin of <italic>Staphylococcus aureus</italic> under sub-minimal inhibitory concentration， and to provide experimental basis for better guidance of clinical medication. Method:The effects of TRQ on the minimum inhibitory concentration （MIC） and bacterial growth of <italic>S.aureus</italic> were determined firstly by microplate method and time-growth curve. The different sub-minimal inhibitory concentrations of TRQ were co-cultured with bacteria or bacterial supernatants， and then co-incubated with defibrillated rabbit blood to detect the inhibitory and neutralizing effects of TRQ on <italic>S.aureus</italic> <italic>α</italic>-hemolysin. Cell counting kit-8 （CCK-8） cell viability assay was used to detect the protective effect of TRQ on <italic>S. aureus</italic>-mediated damage to human alveolar epithelial cells （A549）. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） was used to detect the effect of sub-minimal inhibitory concentration of TRQ on the mRNA expression of <italic>S.aureus</italic> <italic>α</italic>-hemolysin regulatory genes hla and agrA. Result:The MIC of TRQ to <italic>S.aureus </italic>was 1/8 of the stock solution， and the sub-minimal inhibitory concentration （1/64MIC-1/16MIC） TRQ used in this study did not affect the growth of bacteria. 1/64MIC-1/16 MIC TRQ had the effect of inhibiting and neutralizing the hemolytic activity of <italic>α</italic>-hemolysin， with a protective effect on <italic>S.aureus</italic> supernatant-mediated A549 cell damage， and its inhibitory effect on <italic>α</italic>-hemolysin was closely related to the inhibition of hla and agrA mRNA expression. Conclusion:The sub-minimal inhibitory concentration TRQ can inhibit and neutralize the hemolytic activity of <italic>α</italic>-hemolysin of <italic>S.aureus</italic>， with a protective effect on A549 cell damage mediated by <italic>S.aureus</italic> infection， and its mechanism of inhibiting <italic>α</italic>-hemolysin is closely related to the interference with agr regulatory system.