Role of AmpD, OprF and penicillin-binding proteins in beta-lactam resistance in clinical isolates of Pseudomonas aeruginosa

J Med Microbiol. 2007 Jun;56(Pt 6):809-814. doi: 10.1099/jmm.0.47019-0.


In this study, the mechanisms leading to increased chromosomal AmpC beta-lactamase expression and the contributory roles of the outer-membrane protein OprF and penicillin-binding proteins were analysed in 33 characterized clinical isolates of Pseudomonas aeruginosa. The genes ampD and ampE were analysed by PCR and DNA sequencing. Expression of the gene oprF was assessed using real-time RT-PCR, and penicillin-binding proteins were analysed using a chemiluminescence assay. Several of the isolates with increased ampC expression had major deletions affecting ampD, although in some isolates the mechanism of increased ampC expression could not be ascertained. Occasional isolates had increased expression of both ampC and oprF but remained susceptible to cephalosporins, suggesting that increased beta-lactamase activity could not offset increased outer-membrane permeability. There were no discernible changes in penicillin-binding proteins. Genomic deletions in ampD were observed in selected clinical isolates of P. aeruginosa with increased expression of the AmpC beta-lactamase. For some isolates, cephalosporin resistance was dependent upon the interplay of ampC and oprF expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / biosynthesis*
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Proteins / biosynthesis*
  • Bacterial Proteins / genetics
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Gene Expression
  • Humans
  • Luminescent Measurements
  • Membrane Proteins / genetics
  • N-Acetylmuramoyl-L-alanine Amidase / biosynthesis*
  • N-Acetylmuramoyl-L-alanine Amidase / genetics
  • Penicillin-Binding Proteins / biosynthesis*
  • Polymerase Chain Reaction
  • Pseudomonas Infections / microbiology
  • Pseudomonas aeruginosa / drug effects*
  • RNA, Bacterial / biosynthesis
  • RNA, Bacterial / genetics
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Analysis, DNA
  • Sequence Deletion
  • beta-Lactam Resistance / genetics*
  • beta-Lactamases / biosynthesis


  • AmpE protein, Bacteria
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • DNA, Bacterial
  • Membrane Proteins
  • Penicillin-Binding Proteins
  • RNA, Bacterial
  • RNA, Messenger
  • AmpD protein, Bacteria
  • N-Acetylmuramoyl-L-alanine Amidase
  • AmpC beta-lactamases
  • beta-Lactamases