RESUMEN
OBJECTIVE: To evaluate the antibacterial effects of colistin combined with fosfomycin against Klebsiella pneumoniae carbapenemase-producing K. pneumonia in vitro. METHODS: The minimal inhibitory concentration(MIC) of colistin and fosfomycin against 74 strains of KPC-Kp was determined by agar dilution method and broth microdilution method respectively.The fractional inhibitory concentration index(FICI)was calculated by checkerboard method to determine the combined effect. SixKPC-Kp strains were randomly selected to determine the time-killing curves of colistin and fosfomycin alone or in combination. RESULTS: The MIC results polymyxin sensitivity rate of 100%, fosfomycin sensitivity rate of 35.14%. The FIC results In 74 strains, 12.16% synergism, 39.19% section synergism, 6.76% additive effect, 41.89% irrelevant, no antagonism found.The results of time-kill assay showed that there was a significant synergistic effect between colistin and fosfomycin in fosfomycin-sensitive strains, while fosfomycin-resistant strains showed no synergistic effect. CONCLUSION: In the case of fosfomycin-sensitive strains, the combination of colistin and fosfomycin has synergistic effects on KPC-Kp in vitro, and time-kill assay also shows a good synergistic effect. Resistant strains are poor in synergism.