Research on the mechanism of less susceptibility to cefepime than to ceftazidime in clinical isolates of Pseudomonas aeruginosa

doi:10.3969/j.issn.1673-8640.2014.11.023

Abstract

Abstract:

Objective　To investigate the reasons of less susceptibility mechanism to cefepime (FEP) than to ceftazidime (CAZ) in clinical isolates of Pseudomonas aeruginosa. Methods　A total of 60 isolates ofPseudomonas aeruginosa which had been tested being less susceptible to FEP than to CAZ for minimal inhibitory concentration (MIC) by Vitek 2 Compact automatic microorganism analyzer system were collected. Agar dilution method was used to reexamine the MIC of FEP and CAZ. The resistance genes were amplified by polymerase chain reaction (PCR). The expressions of efflux system were analyzed by real-time fluorescence quantitation PCR. Results　The 5% of error rate was showed between agar dilution method and Vitek 2 Compact system. There were isolates with KPC and PSE-1 resistance genes by PCR amplification. There were mainly the expressions of mexB and mexD in efflux system. The sequencing of regulatory genes showed that there were 3 isolates for mexB which the Gly70(GGG) ofnalC was substitute for Glu(GAG)(GGG→GAG) and 2 isolates for mexD which the Gly109(GGC) of nfxB was substitute for Val (GTC)(GGC→GTC). Conclusions　Less susceptibility to FEP than to CAZ in clinical isolates ofPseudomonas aeruginosa is due to the production of KPC and PSE-1 resistance genes and the increasing expression levels of mexAB-OprM and mexCD-OprJ.

Key words: Cefepime, PSE-1, KPC, Efflux system

CLC Number:

R446.5

ZENG Zhangrui, WANG Weiping, HUANG Mei, SHAO Haifeng. Research on the mechanism of less susceptibility to cefepime than to ceftazidime in clinical isolates of Pseudomonas aeruginosa[J]. , 2014, 29(11): 1178-1183.

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