Dissemination of multidrug-resistant Acinetobacter baumannii carrying BlaOₓA₋₂₃ from hospitals in central Taiwan
2013
Lee, Mei-Hui | Chen, Te-Li | Lee, Yi-Tzu | Huang, Lei | Guo, Shuzhen | Yu, Kwok-Woon | Hsueh, Po-Ren | Dou, Horng-Yunn | Su, Ih-Jen | Fung, Chang-Phone
BACKGROUND: 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.
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