Dissemination of IMP-6 metallo-β-lactamase-producing Pseudomonas aeruginosa sequence type 235 in Korea

Objectives: To investigate the epidemiological traits of Pseudomonas aeruginosa clinical isolates producing metallo-β-lactamases (MBLs) in Korea. Methods: A total of 386 non-duplicate P. aeruginosa clinical isolates were collected from Korea in 2009. Detection of MBL genes was performed by PCR. The genetic organization of class 1 integrons carrying the MBL gene cassette was investigated by PCR mapping and sequencing. The epidemiological relationships of the isolates were investigated by multilocus sequence typing and PFGE. Results: Of 386 P. aeruginosa isolates, 30 (7.8%) isolates carried the bla_IMP-6 gene and 1 (0.3%) isolate carried the bla_VIM-2 gene. A probe specific for the bla_IMP-6 gene was hybridized to an ~950 kbp I-CeuI-macrorestriction fragment from all 30 isolates and a probe specific for the bla_VIM-2 gene also hybridized to an ~500 kbp I-CeuI-macrorestriction fragment from 1 isolate (BDC10). All 31 MBL-producing isolates shared an identical sequence type (ST), ST235, and they carried the same bla_OXA-50 allelic type, bla_OXA-50g. All MBL-producing isolates showed similar XbaI-macrorestriction patterns (similarity >85%), irrespective of MBL genotype. Conclusions: P. aeruginosa ST235 carrying the chromosomally located bla_IMP-6 gene is widely disseminated in Korea.