Evaluation Of Different Tigecycline In Vitro Susceptibility Test For Carbapenem-resistant Klebsiella Pneumoniae

Objective:To evaluate different tigecycline in vitro susceptibility test methods for carbapenem-resistant Klebsiella pneumoniae（CRKP）.To understand the resistance of CRKP to tigecycline in Liaoning Province,and provide evidence for clinical drug use more rationally.Methods:A retrospective collection of 269 strains of CRKP isolated from January 2011to December 2016 in several large top hospitals in Liaoning Province.Sensitivity of tigecycline to CRKP was detected by broth microdilution method（BMD）,K-B disk diffusion method,Vitek-2 and E test method.ResμLts:The MIC₅₀ and MIC₉₀ of BMD,E test method and Vitek-2 were as follows:0.5/1μg/mL,0.25/0.5μg/mL and 0.5/4μg/mL.According to the US Food and Drug Administration（FDA）and the European Committee on Antimicrobial Susceptibility Testing（EUCAST）,the sensitivity of CRKP to tigecycline by BMD was97.4%/93.3%,and the intermediate rate was 2.2.%/4.1%,the resistance rate was0.4%/2.6%.The E test method has the highest sensitivity rate of 100%/98.9%,the Vitek-2 has the highest resistance rate of 8.6%/13.4%,and the disk diffusion method has the highest intermediate rate of 11.9%/46.5%.Compared with BMD method,the essential agreement rates（EA）and the categorical agreement rates（CA）of E test method were≥90%,but there is the very major error（VME）of 0.4%/1.9%,respectively.The Vitek-2 EA is only 61.7%,CA is 87.4%/72.1%,the major error（ME）is6.3%/7.4%,and produced no VME.The disk diffusion method CA is only 85.9%/46.5%,the minor error（mE）is 1.9%/2.6%,and the ME is 0.7%/5.6%.A total of 251 CRKP tigecycline MIC<2μg/mL was determined by BMD method.Most of the MIC values measured by E test method were the same as or different from the BMD method by±1dilution.The MIC value measured by Vitek-2 was higher than that of the BMD 1,2,and3 dilutions accounted for 40.2%,27.5%and 10.4%,respectively.Conclusion:The vast majority of CRKP in Liaoning still maintains high sensitivity to tigecycline.For CRKP,E test method,Vitek-2 and disk diffusion method are not suitable for the detection of tigecycline sensitivity alone.Joint detection can be considered and BMD method shoμLd be referred to when resμLts are inconsistent.