Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


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pISSN 2288-0585 eISSN 2288-6850

Chromosomal Mutations in oprD, gyrA, and parC in Carbapenem Resistant Pseudomonas aeruginosa

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2011 December, Volume 14, Issue 4, pages 131-137.

Chromosomal Mutations in oprD, gyrA, and parC in Carbapenem Resistant Pseudomonas aeruginosa

Ji Youn Sung1, Hye Hyun Cho2, Kye Chul Kwon2, Sun Hoe Koo2
1Department of Biomedical Laboratory Science, Far East University, Eumseong, 2Department of Laboratory Medicine, College of Medicine, Chungnam National University, Daejeon, Korea


Background: Outbreaks of carbapenem resistant P. aeruginosa give rise to significant therapeutic challenges for treating nosocomial infections. In this study, we analyzed carbapenem resistance mechanisms in carbapenem resistant and clonally different P. aeruginosa strains. We analyzed chromosomal alterations in the genes of OprD and efflux system regulatory proteins (MexR, NalC, NalD, MexT, and MexZ). We also investigated chromosomal alterations in the quinolone resistance-determining region (QRDR) for quinolone resistance mechanisms.

Methods: Twenty-one clonally different P. aeruginosa strains were isolated by repetitive extragenic palindromic sequence-based PCR (rep-PCR). PCR and DNA sequencing were conducted for the detection of β-lactamase genes and chromosomal alterations of efflux pump regulatory genes, oprD, and QRDR in gyrA, gyrB, parC, and parE.

Results: Only one (P28) of the 21 strains harbored blaVIM-2. Two isolates had mutations in nalD or mexZ that were associated with efflux pump overexpression. Chromosomal alterations causing loss of OprD were found in 4 out of 21 carbapenem resistant P. aeruginosa strains. Nine of 10 imipenem and ciprofloxacin resistant strains had alterations in gyrA and/or parC.

Conclusion: Carbapenem resistance in P. aeruginosa was mediated by several mechanisms, including loss of the OprD, overexpression of efflux systems, and production of carbapenemase. Resistance to quinolone is frequently caused by point mutations in gyrA and/or parC. (Korean J Clin Microbiol 2011;14: 131-137)


 Carbapenem resistant P. aeruginosa, OprD, Efflux system regulatory proteins, QRDR