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This Article Full Text (Papers in Press[PDF]) All Versions of this Article: jmm.0.010017-0v1 58/8/1080    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Zhao, W.-H. Articles by Hu, Z.-Q. PubMed PubMed Citation Articles by Zhao, W.-H. Articles by Hu, Z.-Q. Agricola Articles by Zhao, W.-H. Articles by Hu, Z.-Q.

Relevance of resistance levels to carbapenems and integron-borne bla_IMP-1, bla_IMP-7, bla_IMP-10 and bla_VIM-2 in clinical isolates of Pseudomonas aeruginosa

Showa University School of Medicine

¹ E-mail: whzhao{at}med.showa-u.ac.jp

Received February 4, 2009
Accepted April 15, 2009

The molecular detection and surveillance of the resistant genes harbored by Pseudomonas aeruginosa become more and more important, to assess and control their spread and colonization in hospitals, and to guide treatment of the infections. In this study, we analyzed the resistance mechanisms of carbapenem-resistant clinical isolates of P. aeruginosa and identified the associated integron-borne metallo-β-lactamase (MBL) genes. Twenty-seven imipenem-resistant clinical isolates of P. aeruginosa were divided into three groups according to their resistance levels to carbapenems. Strains bearing bla_IMP-10 showed extremely high level resistance to imipenem with MICs of 512 to 2048 µg ml^-1. By comparison, strains bearing the bla_IMP-1, bla_IMP-7 and bla_VIM-2 showed the middle level of resistance with MICs of 32 to 256 µg ml^-1. The non-MBL-producing strains showed low level of resistance with MICs of 8 to 32 µg ml^-1. The same trend in resistance levels was also observed when resistance to other carbapenems such as meropenem and panipenem were determined. DNA sequencing showed that the MBL gene cassettes were carried by class 1 integrons. The bla_IMP-1, bla_IMP-7 and bla_IMP-10 gene cassettes were preceded by a hybrid P_ant promoter, TGGACA-N₁₇-TAAACT, and the bla_VIM-2 gene cassette was preceded by a weak P_ant promoter, TGGACA-N₁₇-TAAGCT. Most of the MBL genes were linked with one or two resistance genes encoding aminoglycoside-modifying enzymes, such as aac(6')Iae, aac(6')II, aacA7, aacC4, aadA1, aadA2 and aadA6, highlighting the multidrug-resistant properties of these clinical isolates.