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Volume 46, Number 6, December 2013

Dissemination of multidrug-resistant Acinetobacter baumannii carrying BlaOxA-23 from hospitals in central Taiwan 


Mei-Hui Lee, Te-Li Chen, Yi-Tzu Lee, Lei Huang, Shu-Chen Kuo, Kwok-Woon Yu, Po-Ren Hsueh, Horng-Yunn Dou, Ih-Jen Su, Chang-Phone Fung


Received: February 20, 2012    Revised: June 7, 2012    Accepted: August 8, 2012   

 

Corresponding author:

 Shu-Chen Kuo,
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan
Institute of Clinical Medicine, National Yang-Ming University, School of Medicine, Taipei, Taiwan
National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Miaoli County, Taiwan
Corresponding Author InformationCorresponding author. Division of Infectious Diseases, Taipei Veterans General Hospital, No. 201, Sec. 2, Shih-Pai Road, Taipei 112, Taiwan.



 

Background and purpose: 

Imipenem-resistant Acinetobacter baumannii (IRAB) poses a great threat to healthcare systems. Production of carbapenem-hydrolyzing class D β-lactamases (CHDLs) is the major mechanism for imipenem resistance. In this study, we found a high prevalence of IRAB carrying a gene encoding CHDL, blaOxA-23, in central Taiwan and elucidated the molecular characteristics and possible mechanisms of the spread of these isolates. 



 

Methods:

During 2007, we collected 291 nonrepetitive A baumannii isolates from 10 teaching hospitals in Taiwan. The antimicrobial susceptibility of the isolates was determined by agar dilution or Etest. The genes encoding carbapenemase and related structure were detected by polymerase chain reaction mapping and sequencing, and the clonal relationship of the isolates was analyzed by pulsed-field gel electrophoresis. Plasmid localization of blaOxA-23 was determined by extraction of plasmid with commercial kit and Southern blot analysis. 



 

Results:

Among 142 IRAB isolates, 30 harbored the blaOxA-23. The prevalence of IRAB with blaOxA-23 was highest in central Taiwan compared to other areas [24.8% (27/109) vs. 1.6% (3/182); p < 0.001]. These IRAB with blaOxA-23 were also resistant to other antimicrobial agents, except colistin. The PCR methods showed the presence of blaOxA-51 in all isolates. We could exclude clonal spreading due to the diversity of the pulsotype. The blaOxA-23 gene was detected in the plasmids of 6 isolates. Tn2006 was present in 22 (73.3%) isolates, and Tn2008, in 6 other isolates (26.7%). Two strains had blaoxa-23–ΔATPase but lacked upstream ISAba1. 



 

Conclusion:

The high prevalence of blaOxA-23-harboring IRAB in central Taiwan might be attributed to the transposition event of Tn2006. 



 

Key words:

Acinetobacter baumannii, blaOxA-23, Carbapenem resistance, Molecular epidemiology