title: Molecular epidemiology, antimicrobial susceptibility and carbapenemase resistance determinants among Acinetobacter baumannii clinical isolates in Taiwan.
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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Chuang
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Wang-Huei
authors.initials: WH
authors.lastname: Sheng
authors.affiliation: Division of Clinical Research, National Health Research Institutes, Zhunan, Taiwan.
authors.forename: Tsai-Ling
authors.initials: TL
authors.lastname: Lauderdale
authors.affiliation: Center of Research and Diagnostics, Centers for Disease Control, Taipei, Taiwan.
authors.forename: Shu-Yin
authors.initials: SY
authors.lastname: Li
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Jann-Tay
authors.initials: JT
authors.lastname: Wang
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan; Department of Medicine, National Taiwan University, College of Medicine, Taipei, Taiwan.
authors.forename: Yee-Chun
authors.initials: YC
authors.lastname: Chen
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan; Department of Medicine, National Taiwan University, College of Medicine, Taipei, Taiwan. Electronic address: changsc@ntu.edu.tw.
authors.forename: Shan-Chwen
authors.initials: SC
authors.lastname: Chang
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology* / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D016000:Cluster Analysis; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D062486:Public Health Surveillance; D013624:Taiwan / Q000453:epidemiology; D018440:beta-Lactam Resistance / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems
keywords: Acinetobacter; Epidemiology; Genospecies