Dissemination of multidrug-resistant Acinetobacter baumannii carrying BlaOxA-23 from hospitals in central Taiwan.

TLDR: The high prevalence of bla(OxA-23)-harboring IRAB in central Taiwan might be attributed to the transposition event of Tn2006, as well as the possible mechanisms of the spread of these isolates.

Abstract: 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, bla OxA-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 bla OxA-23 was determined by extraction of plasmid with commercial kit and Southern blot analysis. Results Among 142 IRAB isolates, 30 harbored the bla OxA-23. The prevalence of IRAB with bla OxA-23 was highest in central Taiwan compared to other areas [24.8% (27/109) vs. 1.6% (3/182); p bla OxA-23 were also resistant to other antimicrobial agents, except colistin. The PCR methods showed the presence of bla OxA-51 in all isolates. We could exclude clonal spreading due to the diversity of the pulsotype. The bla OxA-23 gene was detected in the plasmids of 6 isolates. Tn 2006 was present in 22 (73.3%) isolates, and Tn 2008 , in 6 other isolates (26.7%). Two strains had bla oxa-23 –ΔATPase but lacked upstream IS Aba1 . Conclusion The high prevalence of bla OxA-23 -harboring IRAB in central Taiwan might be attributed to the transposition event of Tn 2006 .