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Volume 48, Number 1, February 2015

Evolution of carbapenem resistance in Acinetobacter baumannii: An 18-year longitudinal study from a medical center in northern Taiwan 

Wen-Wei Ku, Che-Hsuang Kung, Chi-Hung Lee, Chih-Peng Tseng, Ping-Feng Wu, Shu-Chen Kuo, Te-Li Chen, Yi-Tzu Lee, Fu-Der Wang, Chang-Phone Fung

Received: April 30, 2013    Revised: June 13, 2013    Accepted: July 16, 2013   


Corresponding author:

* Corresponding author. Department of Emergency Medicine, Taipei Veterans General Hospital, Number 201, Section 2, Shih-Pai Road,
Taipei 112, Taiwan.
E-mail address: (Y.-T. Lee). 


Background and purpose: 

Carbapenem-resistant Acinetobacter baumannii has emerged as an important cause of nosocomial infections with high morbidity and mortality. The carbapenemases, especially class D carbapenem-hydrolyzing oxacillinases (CHDLs), play an important role, but the relationship between their prevalence trend and carbapenem resistance remains unclear. 



Between 1995 and 2012, we collected 667 isolates of A. baumannii from a single medical center in northern Taiwan. Pulsed-field gel electrophoresis (PFGE) was used to determine clonality. Antimicrobial susceptibility was determined. Carbapenemase genes and associated genetic structures were detected by polymerase chain reaction.



Isolates were heterogeneous on PFGE. Susceptibility to carbapenem decreased steadily over the study period from 88.1% (2001–2003) to <25% (2010–2012), whereas the isolates remained susceptible to colistin (nearly 100%) and partially susceptible to tigecycline (80%). Starting in 2001, isolates carrying the ISAba1-blaOXA-51-like allele were consistently identified. Isolates containing the transposons Tn2006 or Tn2008 first appeared in 2007 with increasing carriage rates from 17.5% (2007–2009) to 50.0% (2010–2012). The IS1008-ΔISAba3-blaOXA-58-like, blaOXA-72 and metallo-β-lactamase genes were detected only sporadically. Isolates carrying CHDL genes were resistant to multiple drugs, including carbapenem, but remained susceptible to colistin (100.0%). 



Increased carbapenem resistance in A. baumannii may be caused by the increased prevalence of isolates containing the ISAba1-blaOXA-51-like allele and the transposons Tn2006 and Tn2008. 


Key words:

ISAba1-blaOXA-23-like, ISAba1-blaOXA-51-like, Tn2006, Tn2008