Determination of synergistic activities of antibiotics in klebsiella pneumoniae producing colistin-resistant carbapenemase with MALDI-TOF MS

INTRODUCTION AND AIM: In this study, it was aimed to compare the sensitivity and combination synergistic effects for meropenem, colistin, and rifampisin antibiotics in carbapenemase-producing Klebsiella pneumoniae isolates by using MALDI-TOF MS, and also to determine the potential of MALDI TOF as a fast synergy determination method. MATERIALS AND METHODS: Isolated in Sakarya University Training and Research Hospital Medical Microbiology Laboratory between 2014 and 2020. and 20 colistin resistant K. pneumoniae isolates genotypically determined by real-time Polymerase Chain Reaction method (Gene Xpert Carba-R kit, Cepheid, USA) were included in the study. The synergistic effect of each strain was investigated by the combination of colistin + meropenem and colistin + rifampisin, checkerboard microdilution which gives qualitative results and MALDI-TOF MS (bioMerieux, France) method which gives quantitative results under in-vitro conditions. The MALDI-TOF MS device has been studied in the mass range of 10 to 1000 kDa m / z. Then, the presence of peaks between 446.73 m / z and 660.12 m / z was observed. According to the data obtained, the isolates showing synergistic effect were compared with the results of the reference method, Checkerboard microdilution method. RESULTS: Synergistic effects were detected in 9 out of 20 strains in which the effectiveness of colistin + meropenem combination was investigated with the checkerboard method, and in 17 of 20 strains for colistin + rifampicin combination. In MALDI-TOF MS method, synergy was detected in 14 out of 20 strains for colistin + meropenem combination and in 12 out of 20 strains for colistin + rifampicin combination. CONCLUSION: When we compared the results of the MALDI-TOF MS method and the reference Checkerboard microdilution method in resistant strains, 6 of 11 strains (66,6%) showed synergistic harmony in colistin + meropenem combined drug interaction, while 16 strains in colistin + rifampisin combined drug interaction showed 11 Synergistic harmony was observed in (68,7%). The MALDI-TOF MS system appears to be a fast reliable method for synergy determination. Further and comprehensive studies are required.