Abstract:

Objective To analyze the susceptibility of tigecycline against carbapenems-resistant Klebsiella pneumoniae and Acinetobacter baumannii and the methods for in vitro susceptibility test. Methods A total of 61 isolates,including 41 isolates of Acinetobacter baumannii and 20 isolates of Klebsiella pneumoniae,were collected in the Tenth People's Hospital of Tongji University from November 2013 to February 2014. The isolates were confirmed as carbapenems-resistant isolates by Vitek 2 compact automatic microbiological analysis system and disk diffusion method. The broth microdilution method,minimum inhibitory concentration（MIC） method and disk diffusion method were used to determine the susceptibility of tigecycline. Results For carbapenems-resistant Acinetobacter baumannii,the MIC₅₀ and MIC₉₀ of tigecycline by broth microdilution method were 2 and 4 mg/ L. According to the U. S. Food and Drug Administration（FDA） criterion,the resistance rate,intermediary rate and sensitivity rate were 7.3%,29.3% and 63.4%,respectively. Compared with broth microdilution method,the essential agreement（EA） and categorical agreement（CA） of MIC method were 97.6% and 87.8%,and there was no very major error（VME） and major error（ME）,and the minor error（mE） accounted for 12.2%. The CA of disk diffusion method was 24.4%,and there was no VME,the ME accounted for 7.3%,and the mE accounted for 68.3%. For carbapenems-resistant Klebsiella pneumoniae,the MIC₅₀ and MIC₉₀ of tigecycline by broth microdilution method were 1 and 2 mg/L. According to the FDA criterion,the resistance rate,intermediary rate and sensitivity rate were 5.0%,0.0% and 95.0%,respectively. Compared with broth microdilution method,the EA and CA of MIC method accounted for 95.0%. There was no VME and ME,and the mE accounted for 5.0%. The CA of disk diffusion method was 30.0%,VME and ME did not appear,and mE accounted for 70.0%. Conclusions Tigecycline against carbapenems-resistant Klebsiella pneumoniae has good antibacterial activity,while the antibacterial activity of carbapenems-resistant Acinetobacter baumannii decreases. For carbapenems-resistant Klebsiella pneumoniae,the MIC method could be used for routine clinical determination of tigecycline susceptibility or confirmation,while for carbapenems-resistant Acinetobacter baumannii,the results of MIC method need to be treated with caution,and should be confirmed by broth microdilution method if necessary. The evaluation indicators do not support the use of disk diffusion method for tigecycline susceptibility test.

Key words: Tigecycline, Carbapenems-resistant Klebsiella pneumoniae, Carbapenems-resistant Acinetobacter baumannii, Susceptibility test