Selective advantages of two major clones of carbapenem-resistant Pseudomonas aeruginosa isolates (CC235 and CC641) from Korea: antimicrobial resistance, virulence and biofilm-forming activity.

The characteristics of carbapenem-resistant P. aeruginosa (CRPA) isolates from Korea were investigated. Two major clones, clonal complex (CC) 235 and CC641, were identified. CC235, an important international clone, might have been imported recently in Korea as this clone displayed a homogeneous genotype, oprD mutation and antimicrobial resistance profile. While 13 ST235 isolates harboured the blaIMP-6 gene, which conferred high-level meropenem resistance, CC641 isolates showed high biofilm-forming activity. CC235 and CC641 isolates showed distinct distribution of ferripyoverdine receptor type and virulence markers. While all CC235 isolates were of the fpvAIIb type and exoS(-)/exoU(+), CC641 isolates were exoS(+)/exoU(-), and all but one showed the fpvAIII type. CC235 and CC641 isolates were also characterized by different extracellular protease activity: staphylolysin and elastase activities in CC235 and CC641, respectively. Two major CRPA clones in Korea seem to be predominant, reflecting their selective advantage by virtue of antimicrobial resistance, virulence and biofilm-forming activity.