Efflux system overexpression and decreased OprD contribute to the carbapenem resistance among extended-spectrum beta-lactamase-producing Pseudomonas aeruginosa isolates from a Chinese university hospital

Microb Drug Resist. 2013 Dec;19(6):463-8. doi: 10.1089/mdr.2013.0010. Epub 2013 Jul 18.

Abstract

The aim of this study was to investigate, for the first time, the combinations of carbapenem resistance mechanisms in clinical isolates of extended-spectrum beta-lactamase (ESBL)-producing Pseudomonas aeruginosa in a Chinese hospital. Pulsed-field gel electrophoresis revealed the presence of eight clonal types among the 15 ESBL producers. Multilocus sequence typing of two isolates harboured blaIMP-1 identified the clonal strain as ST325. All these genes were found either alone or simultaneously in the strains in the following five different arrangements:<blaOXA-10>; <blaOXA-10, blaIMP-1>; <blaPER-1, blaOXA-10>; <blaPER-1, blaPSE-1>; <blaOXA-10, blaTEM-1>. Regarding mutation-driven resistance, all, but four of the isolates had a relevant decrease of oprD expression. In addition, 73.3% of the isolates overexpressed mexB, 40% mexD, and 33.3% mexY. A specific combination of overexpressed mexB or mexY and alteration in loop L710 of OprD were significantly associated with meropenem resistance. In conclusion, combination of several mutation-driven mechanisms leading to OprD inactivation and overexpression of efflux systems was the main carbapenem resistance mechanism among the ESBL-producing P. aeruginosa isolates, but acquisition of a transferable resistance determinant such as metallo-β-lactamase could be problematic in clinical settings in China.

MeSH terms

  • Anti-Bacterial Agents / therapeutic use
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Carbapenems / therapeutic use
  • China
  • Clone Cells
  • Gene Expression Regulation, Bacterial*
  • Gene Transfer, Horizontal
  • Genes, MDR*
  • Hospitals, University
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Multilocus Sequence Typing
  • Plasmids
  • Porins / genetics*
  • Porins / metabolism
  • Pseudomonas Infections / drug therapy
  • Pseudomonas Infections / microbiology
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / genetics*
  • Pseudomonas aeruginosa / isolation & purification
  • beta-Lactam Resistance / genetics*
  • beta-Lactamases / genetics*
  • beta-Lactamases / metabolism

Substances

  • Anti-Bacterial Agents
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carbapenems
  • Membrane Proteins
  • Membrane Transport Proteins
  • MexB protein, Pseudomonas aeruginosa
  • MexD protein, Pseudomonas aeruginosa
  • MexXY protein, Pseudomonas aeruginosa
  • Porins
  • OprD protein, Pseudomonas aeruginosa
  • beta-Lactamases