[Synergistic antibacterial effect and mechanisms of dihydroartemisinin and cefuroxime incombination].

In this study, we explored the antibacterial effect and mechanism of dihydroartemisinin(DHA) combined with cefuroxime(CFX) or ampicillin against Escherichia coli. The minimum inhibitory concentration(MIC) of DHA, cefuroxime, and ampicillin against E. coli was 300,25,25 μmol·L(-1), respectively, determined by broth microdilution method and 2,3,5-triphenyltetrazolium chloride(TTC) method. The minimum bactericidal concentration(MBC) was 25 μmol·L(-1) for cefuroxime, above 600 μmol·L~(-1) for DHA. The fractional inhibitory concentration index(FICI) of DHA combined with cefuroxime or ampicillin was 0.375 and 0.75, respectively, determined by checkerboard microdilution assay, suggesting the synergistic effect or additive effect of the drug combination. Moreover, the time-effect curve showed that the antibacterial activity of DHA and CFX combination was much stronger than that of either of the drugs, suggesting that combination with DHA can decrease the CFX dosage. Then we studied the synergistic mechanism of DHA combined with cefuroxime and found that the combination of the two drugs had a significant inhibitory effect on the total protein bands, as shown by the results of polypropylene gel electrophoresis. The results of conductivity method and alkaline phosphatase test respectively showed that its conductivity value and alkaline phosphatase(AKP) leak were significantly higher than either of the drugs, suggesting that the integrity of bacteria may be damaged. The scanning electron microscope(SEM) results showed that the morphology of E. coli was destroyed most in the combination group. The quantitative fluorescence PCR technology showed that the combination of two drugs can inhibit the expression of superoxide stress gene soxS. In summary, the combination of dihydroartemisinin and cefuroxime has a synergistic antibacterial effect on E. coli.