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

J Microbiol Immunol Infect. 2014 Aug;47(4):324-32. doi: 10.1016/j.jmii.2013.03.008. Epub 2013 May 28.

Abstract

Background: 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 bla(OxA-51) (n = 135), followed by bla(OxA-24) (n = 4), bla(OxA-23) (n = 2), and bla(OxA-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.

Keywords: Acinetobacter; Epidemiology; Genospecies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter Infections / epidemiology*
  • Acinetobacter Infections / microbiology*
  • Acinetobacter baumannii / drug effects*
  • Acinetobacter baumannii / genetics*
  • Acinetobacter baumannii / isolation & purification
  • Anti-Bacterial Agents / pharmacology*
  • Carbapenems / pharmacology*
  • Cluster Analysis
  • Electrophoresis, Gel, Pulsed-Field
  • Genotype
  • Humans
  • Microbial Sensitivity Tests
  • Multilocus Sequence Typing
  • Public Health Surveillance
  • Taiwan / epidemiology
  • beta-Lactam Resistance / genetics*

Substances

  • Anti-Bacterial Agents
  • Carbapenems