Effect of clove oil combined with quinolones antibiotics on methicillin-resistant Staphylococcus aureus / 中草药

ABSTRACT

Objective: To investigate the anti-methicillin-resistant Staphylococcus aureus (MRSA) activity of clove oil combined with quinolones antibiotics in vitro, and provide scientific evidences for the treatment of MRSA infection by clove oil combined with quinolones antibiotics. Methods: Minimal inhibitory concentrations (MICs) of clove oil and four quinolones antibiotics (moxifloxacin, levofloxacin, ciprofloxacin and norfloxacin) were determined by microdilution method; Fractional inhibitory concentration (FIC) indexes of clove oil combined with four quinolones antibiotics were determined by chessboard dilution method; Inhibition effect of MRSA by clove oil combined with four quinolones antibiotics was analyzed by growth curve method. MIC changes were analyzed when MRSA standard strain ATCC33591 was induced 30 generations with clove oil. Results: A total of 35 strains of MRSA isolated from clinical patients showed that the highest resistance rate was moxifloxacin (88.57%), followed by ciprofloxacin and levofloxacin (77.14%), and the lowest resistance rate was norfloxacin (74.29%). The results of FIC index analysis showed that the different thesynergistic action effects of clove oil with moxifloxacin, levofloxacin, ciprofloxacin and ornorfloxacin, were 42.86%, 37.15%, 34.28% and 34.28%, respectively; The additive effects of which were 28.57%, 25.71%, 22.86% and 42.86%, respectively; The unrelated effects of that were 28.57%, 20.00%, 42.86% and 22.86%, respectively. Among them, there was partial antagonism in experimental strains when combined with levofloxacin, accounting for 17.14%. The growth curve showed that the combination of clove oil and quinolone antibiotics had a significant synergistic inhibition on MRSA. The results of induced drug resistance test showed that MIC did not change after 30 generations of continuous induction with the clove oil, but increased to 16 times of that of ciprofloxacin under the same condition, which indicated that the clove oil was not easy to make MRSA resistant. Conclusion: Clove oil is not easy to produce drug resistance. They showed different interactions on each other when clove oil combined with quinolones antibiotics, and most strains of MRSA isolated from clinical patients had obvious synergistic and additive inhibition effect. The dosage of quinolones antibiotics could be cut when clove oil combined with quinolones antibiotics for treating MRSA infection.