Analysis for drug sensitivity of 11 antimicrobial in vitro combination regimenagainst carbapenem-resistant Enterobacteriaceae
Objective To observe the susceptibility test result in vitro of the combination of two drugs to carbapenem-resistant Enter-obacteriaceae(CRE)for screening the effective anti-infective therapy.Methods A total of 60 CRE strains which were isolated from the specimens from the clinic of Qingdao Eighth People's Hospital from January 2023 to December 2023.Carbapenem enzyme type was detected by colloidal gold immunochromatography.The minimal inhibitory concentration(MIC)was determined by micro broth dilution method.Ceftazidime/avibactam(CZA)combined with aztreonam(ATM),COL combined with tigecycline(TGC),meropenem(MEM),cefoperazone/sulbactam(SCF),amikacin(AK)and levofloxacin(LEV),TGC combined with MEM,SCF and AK,MEM combined with SCF and ertapenem(ETP)were performed by the checkerboard dilution method respectively.Fractional inhibitory con-centration(FIC)index was used to determine the combined effects.Results Carbapenem enzyme was detected in all the 60 CRE strains,including 49 Klebsiella pneumoniae carbapenemases(KPC)-type,10 New Delhi metallo-β-lactamase(NDM)-type and 1 Imi-penem enzyme(IMP)-type.The MICs of CZA to 49 KPC-producing strains were ≤8 mg/L,showing all sensitive,and to 11 NDM-and IMP-producing strains were＞128 mg/L,showing all resistant.The synergy rate of CZA was 100％after combining with ATM.MEM combined with SCF had the highest synergy rate of 63.4％,and the sum of synergistic rate and addition rate was 96.7％.The syn-ergistic rate and additive rate of TGC combined with AK were the lowest,which was 31.7％.Among KPC and NDM enzyme types strains,the sum of synergy rate and addition rate of MEM combined with SCF were the highest,which were 100.0％and 80.0％respec-tively.The sum of synergy rate and addition rate of COL combined with LEV were the lowest,which were 32.6％and 30.0％.None of the 11 combination regimens showed antagonistic effect.The MICrange,MIC50 and MIC90 of combination regimens for CRE strains were decreased to some extent compared with those of each single drug.Conclusion CZA alone or in combination with ATM were effective for CRE strains.The MEM combined with SCF had the highest synergy rate and addition rate,which could provide reference for clinical experience medication.
carbapenem resistant Enterobacteriaceaecheckerboard testingcombined antimicrobial susceptibility testfractional in-hibitory concentration index
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