Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain.
Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
J Antimicrob Chemother. 2017 Feb;72(2):448-454. doi: 10.1093/jac/dkw456. Epub 2016 Dec 20.
To evaluate the interconnection between peptidoglycan (PG) recycling, fosfomycin susceptibility and synergy between fosfomycin and β-lactams in Pseudomonas aeruginosa METHODS: Fosfomycin MICs were determined by broth microdilution and Etest for a panel of 47 PAO1 mutants defective in several components of PG recycling and/or AmpC induction pathways. PAO1 fosfomycin MICs were also determined in the presence of a 5 mM concentration of the NagZ inhibitor PUGNAc. Population analysis of fosfomycin susceptibility and characterization of the resistant mutants that emerged was also performed for selected strains. Finally, fosfomycin, imipenem and fosfomycin + imipenem killing curves were assessed.
Mutants defective in AmpG, NagZ or all three AmpD amidases showed a marked increase in fosfomycin susceptibility (at least two 2-fold dilutions with respect to WT PAO1). Moreover, PAO1 fosfomycin MICs were consistently reduced from 48 to 24 mg/L in the presence of a 5 mM concentration of PUGNAc. Fosfomycin hypersusceptibility of the ampG, nagZ and triple ampD mutants was also clearly confirmed in the performed population analysis, although the emergence of resistant mutants, through GlpT mutations, was not avoided. Synergy between fosfomycin and imipenem was evidenced for the WT strain, the AmpC-hyperproducing strain (triple AmpD mutant) and the NagZ and AmpG mutants in killing curves. Moreover, regrowth of resistant mutants was not evidenced for the combination.
PG recycling inhibitors are envisaged as useful adjuvants in the treatment of P. aeruginosa infections with β-lactams and fosfomycin and therefore further development of these molecules is encouraged.
评估肽聚糖 (PG) 循环、磷霉素敏感性以及磷霉素与β-内酰胺类抗生素之间协同作用在铜绿假单胞菌中的相互关系。
采用肉汤微量稀释法和 Etest 法测定了一组 47 株 PAO1 突变株对几种 PG 循环和/或 AmpC 诱导途径成分缺陷的磷霉素 MIC。还在 5mM NagZ 抑制剂 PUGNAc 存在的情况下测定了 PAO1 磷霉素 MIC。还对选定菌株进行了磷霉素药敏性的群体分析和耐药突变体的特征描述。最后，评估了磷霉素、亚胺培南和磷霉素+亚胺培南的杀菌曲线。
AmpG、NagZ 或所有三种 AmpD 酰胺酶缺陷突变株对磷霉素的敏感性显著增加（与野生型 PAO1 相比至少增加了两个 2 倍稀释度）。此外，在 5mM PUGNAc 浓度存在的情况下，PAO1 磷霉素 MIC 从 48 降至 24mg/L。在进行的群体分析中，ampG、nagZ 和三重 ampD 突变株的磷霉素超敏性也得到了明确证实，尽管通过 GlpT 突变无法避免耐药突变体的出现。在杀菌曲线中，WT 菌株、AmpC 过度产生菌株（三重 AmpD 突变株）以及 NagZ 和 AmpG 突变株均显示出磷霉素与亚胺培南之间的协同作用。此外，组合中未发现耐药突变体的再生长。
PG 循环抑制剂被视为治疗铜绿假单胞菌感染的β-内酰胺类抗生素和磷霉素的有用辅助剂，因此鼓励进一步开发这些分子。
