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Volume 47, Number 4, August 2014

Molecular epidemiology, antimicrobial susceptibility and carbapenemase resistance determinants among Acinetobacter baumannii clinical isolates in Taiwan 


Yu-Chung Chuang, Wang-Huei Sheng, Tsai-Ling Lauderdale, Shu-Yin Li, Jann-Tay Wang, Yee-Chun Chen, Shan-Chwen Chang


Received: October 9, 2012    Revised: January 25, 2013    Accepted: March 27, 2013   

 

Corresponding author:

Shan-Chwen Chang, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
Department of Medicine, National Taiwan University, College of Medicine, Taipei, Taiwan
Corresponding Author InformationCorresponding author. Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei 100, Taiwan. 



 

Background and purpose: 

Emerging carbapenem resistance among Acinetobacter baumannii clinical isolates is a worldwide problem. Infections caused by A. baumannii are increasing and demonstrate high mortality rates. This study aimed to establish a nationwide surveillance of antimicrobial susceptibility, carbapenemase genes, and clonal relationships of A. baumannii clinical isolates in Taiwan. 



 

Methods:

Clinical isolates of Acinetobacter calcoaceticus–A. baumannii (ACB) complex collected by the Taiwan Surveillance of Antimicrobial Resistance-V program between July 2006 and September 2006 were used in this study. Genospecies identification was verified by 16S-23S rRNA intergenic-spacer sequences. Carbapenemase genes were detected by polymerase chain reaction. Pulsed-field gel electrophoresis and multilocus sequence typing (MLST) was applied for identification of clonal relationships. 



 

Results:

Among the 151 ACB-complex isolates collected, 134 (88.7%) were A. baumannii, 12 (8.0%) were A. pittii, and five (3.3%) were A. nosocomialis. A. baumannii isolates showed higher resistance rates to ciprofloxacin, amikacin, and ampicillin/sulbactam than A. pittii or A. nosocomialis (all p < 0.001). The most commonly detected carbapenemase genes were blaOxA-51 (n = 135), followed by blaOxA-24 (n = 4), blaOxA-23 (n = 2), and blaOxA-58 (n = 1). Three major A. baumannii clones were found throughout Taiwan, and showed significantly higher resistance rates to ciprofloxacin, amikacin, and ampicillin/sulbactam than the other A. baumannii isolates (100% vs. 68.7%, p < 0.001; 98.4% vs. 61.5%, p < 0.001; and 66.7% vs. 39.8%, p = 0.004; respectively). MLST showed that these major clones were sequence type 2 and belonged to international clonal complex 2. 



 

Conclusion:

Our results demonstrate clonal spreading of A. baumannii in Taiwan hospitals and that these clones were more resistant to many antimicrobial agents. Efforts to prevent and control A. baumannii colonization/infections and prudent use of antibiotics to reduce antimicrobial selective pressure should be emphasized. 



 

Key words:

Acinetobacter, Epidemiology, Genospecies