Subtractive Effect Of Dihydromyricetin On Drug Resistance Of Menicillin Resistant Staphylococcus Aureus

Methicillin resistant Staphylococcus aureus(MRSA)is one of the pathogens with the most serious drug resistance and the most difficult to cure in the world.Traditional antibiotics can not solve the diseases caused by the drug-resistant bacteria.Finding effective antibacterial substances from natural drugs is an important direction for the development of new antibiotics.Based on the previous research in the laboratory,dihydromyricetin(DMY)was selected from several traditional Chinese medicine monomers,which cooperated with ceftiofur hydrochloride(CEF)to effectively reduce the drug resistance of MRSA.The safety and effectiveness of its combined effect were investigated through cytotoxicity test and animal infection model.Four kinds of traditional Chinese medicine monomers procyanidins,DMY,cyanidin-3-o-glucoside and Mongolian,which could combination of β-lactam antibiotics were screened by micro broth dilution method and checkerboard method.The results showed that the FICI of DMY combined with CEF on MRSA ATCC33591 was 0.5,showing a synergistic antibacterial effect,and the FICI on against 19 clinical MRSA strains was 0.1875 ～ 0.375.When the concentration of 32 μg/m L of DMY could reduce the MBC of CEF to ATCC33591 by 16 times(256 μg/m L→16 μg/m L);The time kill curve results show that 64 μg/m L of DMY combined action with CEF at 128 μg/m L could kill all MRSA.The cell safety of DMY,CEF and their combination on IPEC-J 2,Raw 264.7,SW 480 and A 549 was evaluated by CCK-8 method.The results show that DMY at 32 μg/m L had good safety for four kinds of cells,and the cell viability was 100%,and the DMY was 64 ～ 128 μg/m L had the least effect on the cell viability of A 549,followed by IPEC-J 2,Raw 264.7 and SW 480.DMY combined with CEF did not increase cytotoxicity,and there was no difference with DMY alone.Through the therapeutic test of DMY and CEF alone and in combination on the abdominal cavity model of MRSA infected mice,it is verified that compared with CEF alone,the therapeutic effect of DMY combined with CEF on the MRSA infected model in vivo is better than that of CEF alone,and the therapeutic effect on the lung of mice is the most obvious.Compared with DMY group alone,the therapeutic effect of DMY combined with CEF was slightly better than that of DMY group alone.In summary,this study screened that the traditional Chinese medicine monomer DMY and CEF have good synergistic effect on MRSA in vitro and good safety.The therapeutic effect of DMY combined with CEF on MRSA in vivo is better than that of CEF alone.This study can provide a solution for the reduction of bacterial drug resistance of MRSA and provide data support for the development of clinical combination of DMY and CEF.