RT Journal Article SR Electronic(1) A1 Bratu, Simona A1 Landman, David A1 Gupta, Jyoti A1 Quale, JohnYR 2007 T1 Role of AmpD, OprF and penicillin-binding proteins in β-lactam resistance in clinical isolates of Pseudomonas aeruginosa JF Journal of Medical Microbiology, VO 56 IS 6 SP 809 OP 814 DO https://doi.org/10.1099/jmm.0.47019-0 PB Microbiology Society, SN 1473-5644, AB In this study, the mechanisms leading to increased chromosomal AmpC β-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 β-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 β-lactamase. For some isolates, cephalosporin resistance was dependent upon the interplay of ampC and oprF expression., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.47019-0