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Volume 42, Number 4, August 2009

Prevalence of extended-spectrum β-lactamases in Enterobacter cloacae in Taiwan and comparison of 3 phenotypic confirmatory methods for detecting extended-spectrum β-lactamase production


Jia-Ling Yang, Jann-Tay Wang, Tsai-Ling Lauderdale, Shan-Chwen Chang
J Microbiol Immunol Infect. 2009;42:310-316.

Received: May 1, 2008    Revised: June 4, 2008    Accepted: July 4, 2008   

 

Corresponding author:

Shan-Chwen Chang, Department of Internal Medicine, National Taiwan University Hosptial, No. 7 Chung-Shan South Rd., Taipei 100, Taiwan.



 

Background and purpose: 

The prevalence of extended-spectrum β-lactamases (ESBLs) in Enterobacter cloacae remains unclear in Taiwan. This study was conducted to investigate the prevalence of ESBL-producing E. cloacae in Taiwan.



 

Methods:

 116 clinical isolates of E. cloacae were tested for cefepime susceptibility. Isolates with a minimal inhibitory concentration (MIC) of >=0.25 ug/mL for cefepime were tested for the ESBL phenotype by the combination-disk synergy tests (CDSTs) using cefotaxime and ceftazidime alone or in combination with clavulanic acid, the ESBL Etest using cefepime with or without clavulanic acid, and the double-disk synergy test (DDST) using cefepime and amoxicillin-clavulanate.



 

Results:

 Thirty eight isolates had an MIC of >=0.25 ug/mL for cefepime. Of these, 27 had an ESBL phenotype; 24 were determined by DDST, 25 by CDST, and 21 by ESBL Etest. ESBL genes were identified in 24 isolates. One isolate without and ESBL phenotype but with an MIC of >=0.25 ug/mL for cefepime was confirmed to have the ESBL gene. DDST, DESTs, and ESBL Etest detected 24, 22, and 21 of 24 isolates with the ESBL genotype, respectively. DDST had the highest sensitivity of 96.0% for detecting ESBLs among isolates and a specificity of 69.2%. CDSTs and ESBL Etest had sensitivities of 88.0% and 84.0%, respectively and specificities of 69.2% and 100%, respectively. The overall prevalence of ESBL-producing E. cloacae was 21.6%.



 

Conclusion:

 A combination of DDST using cefepime and amoxicillin-clavulanate and CDSTs using cefotaxime and ceftazidime alone or in combination with clavulanic acid enhance the detection of ESBL production in Taiwan.



 

Key words:

 beta-Lactamases; Enterobacter cloacae; Prevalence; Taiwan