RESUMEN
Aim To study the change of mutant pre- vention concentration (MPC) in carbapenem-resistant Acinetobacter baumannii (CRAB) treated with moxi- floxacin ( MFX ) and/ or cefoperazone/ sulbactam (CFS) in vitro, and provide a theoretical support for preventing the bacterial resistance. Methods To cal- culate the fractional inhibitory concentration (FIC) in- dex, the minimum inhibitory concentration (MIC) of 20 clinical isolates of CRAB treated with MFX and/ or CFS was determined by checkerboard microdilution as- say. In addition, to calculate the selection index (SI), the MPC of 20 clinical isolates of CRAB treated with MFX and/ or CFS was determined by agar plate di- lution assay. Results Our study showed that there was synergistic/ addictive action, rather than antago- nism action against clinical isolates of CRAB when treated with MFX + CFS. The SI of the 20 isolates trea- ted with MFX or CFS alone was 4 ~128 and 8 ~64 re- spectively, but reduced to 1 ~8 and 4 ~16 when trea- ted with MFX + CFS, which decreased by 2 ~16 and 2 ~4 times respectively compared with the single treat- ment. Conclusion These results suggest that the combination treatment of MFX + CFS against clinical isolates of CRAB might lower the MPC of the isolates treated with MFX/ CFS alone, narrow the mutant selec- tion window, and prevent the generation of drug - re- sistant mutants.