Bratu Simona, Landman David, Gupta Jyoti, Quale John
Division of Infectious Diseases, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
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.
在本研究中，对33株已鉴定的铜绿假单胞菌临床分离株分析了导致染色体AmpCβ-内酰胺酶表达增加的机制以及外膜蛋白OprF和青霉素结合蛋白的作用。通过PCR和DNA测序分析ampD和ampE基因。使用实时RT-PCR评估oprF基因的表达，并使用化学发光分析法分析青霉素结合蛋白。几株ampC表达增加的分离株有影响ampD的大片段缺失，尽管在一些分离株中ampC表达增加的机制尚无法确定。偶尔有分离株ampC和oprF表达均增加，但对头孢菌素仍敏感，这表明β-内酰胺酶活性增加无法抵消外膜通透性增加的影响。青霉素结合蛋白没有明显变化。在AmpCβ-内酰胺酶表达增加的铜绿假单胞菌特定临床分离株中观察到ampD的基因组缺失。对于一些分离株，头孢菌素耐药性取决于ampC和oprF表达的相互作用。
