Molecular characterization of metallo-β-lactamase-producing Acinetobacter baumannii and Acinetobacter genomospecies 3 from Korea: Identification of two new integrons carrying the ^bla_VIM-2 gene cassettes

Carbapenem-resistant Acinetobacter spp. used to be rare, but are increasingly isolated in Korea. Among 28 isolates of imipenem-resistant Acinetobacter spp. found in a Korean hospital in 1998 and 1999, 14 produced metallo-β-lactamases. The bla_VIM-2 gene was detected, by PCR, in 11 and two isolates of Acinetobacter baumannii and Acinetobacter genomospecies 3, respectively, and bla_IMP-1 in one isolate of A. baumannii. The MICs of imipenem for the isolates were 8-32 mg/L. PFGE analysis of SmaI-digested genomic DNA gave identical patterns in eight of 11 bla_VIM-2-positive A. baumannii isolates from respiratory specimens of ICU patients. The bla_VIM-2 gene cassettes in the isolates are identical to those from Pseudomonas aeruginosa isolates in Europe, but are inserted into new class I integrons In105 and In106. The attC site of the last cassette of the array in In106 is interrupted by the insertion of a putative class II intron. This is the first report of VIM-2 β-lactamase-producing A. baumannii and Acinetobacter genomospecies 3. Production of the VIM-2 enzyme presents an emerging threat of carbapenem resistance among Acinetobacter spp. in Korea.