Ballestero-Téllez M, Docobo-Pérez F, Portillo-Calderón I, Rodríguez-Martínez J M, Racero L, Ramos-Guelfo M S, Blázquez J, Rodríguez-Baño J, Pascual A
Unidad intercentros de Enfermedades Infecciosas, Microbiología y Medicina Preventiva, Hospital Universitario Virgen Macarena, Sevilla, Spain.
Instituto de Biomedicina de Sevilla, IBiS/Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, Spain.
J Antimicrob Chemother. 2017 May 1;72(5):1303-1309. doi: 10.1093/jac/dkw573.
Fosfomycin activity in Escherichia coli depends on several genes of unknown importance for fosfomycin resistance. The objective was to characterize the role of uhpT , glpT , cyaA and ptsI genes in fosfomycin resistance in E. coli.
WT E. coli BW25113 and null mutants, Δ uhpT , Δ glpT , Δ cyaA , Δ ptsI , Δ glpT-uhpT , Δ glpT-cyaA , Δ glpT-ptsI , Δ uhpT-cyaA , Δ uhpT-ptsI and Δ ptsI-cyaA , were studied. Susceptibility to fosfomycin was tested using CLSI guidelines. Fosfomycin mutant frequencies were determined at concentrations of 64 and 256 mg/L. Fosfomycin in vitro activity was tested using time-kill assays at concentrations of 64 and 307 mg/L (human C max ).
Fosfomycin MICs were: WT E. coli BW25113 (2 mg/L), Δ glpT (2 mg/L), Δ uhpT (64 mg/L), Δ cyaA (8 mg/L), Δ ptsI (2 mg/L), Δ glpT-uhpT (256 mg/L), Δ glpT-cyaA (8 mg/L), Δ glpT-ptsI (2 mg/L), Δ uhpT-cyaA (512 mg/L), Δ uhpT-ptsI (64 mg/L) and Δ ptsI-cyaA (32 mg/L). In the mutant frequency assays, no mutants were recovered from BW25113. Mutants appeared in Δ glpT , Δ uhpT , Δ cyaA and Δ ptsI at 64 mg/L and in Δ uhpT and Δ cyaA at 256 mg/L. Δ glpT-ptsI , but not Δ glpT-cyaA , Δ uhpT-cyaA or Δ uhpT-ptsI , increased the mutant frequency compared with the highest frequency found in each single mutant. In time-kill assays, all mutants regrew at 64 mg/L. Initial bacterial reductions of 2-4 log 10 cfu/mL were observed for all strains, except for Δ uhpT-ptsI , Δ glpT-uhpT and Δ uhpT-cyaA . Only Δ glpT and Δ ptsI mutants were cleared using 307 mg/L.
Fosfomycin MIC may not be a good efficacy predictor, as highly resistant mutants may appear, depending on other pre-existing mutations with no impact on MIC.
磷霉素在大肠杆菌中的活性取决于几个对磷霉素耐药性重要性未知的基因。目的是阐明uhpT、glpT、cyaA和ptsI基因在大肠杆菌对磷霉素耐药性中的作用。
研究了野生型大肠杆菌BW25113及其缺失突变体ΔuhpT、ΔglpT、ΔcyaA、ΔptsI、ΔglpT - uhpT、ΔglpT - cyaA
、ΔglpT - ptsI、ΔuhpT - cyaA、ΔuhpT - ptsI和ΔptsI - cyaA。使用CLSI指南检测对磷霉素的敏感性。在64和256mg/L浓度下测定磷霉素突变频率。使用时间杀菌试验在64和307mg/L（人Cmax）浓度下测试磷霉素的体外活性。
磷霉素的MIC分别为：野生型大肠杆菌BW25113（2mg/L）、ΔglpT（2mg/L）、ΔuhpT（64mg/L）、ΔcyaA（8mg/L）、ΔptsI（2mg/L）、ΔglpT - uhpT（256mg/L）、ΔglpT - cyaA（8mg/L）、ΔglpT - ptsI（2mg/L）、ΔuhpT - cyaA（512mg/L）、ΔuhpT - ptsI（64mg/L）和ΔptsI - cyaA（32mg/L）。在突变频率测定中，未从BW25113中回收突变体。在64mg/L时，ΔglpT、ΔuhpT、ΔcyaA和ΔptsI中出现突变体，在256mg/L时，ΔuhpT和ΔcyaA中出现突变体。与每个单突变体中发现的最高频率相比，ΔglpT - ptsI增加了突变频率，但ΔglpT - cyaA、ΔuhpT - cyaA或ΔuhpT - ptsI没有。在时间杀菌试验中。所有突变体在64mg/L时都重新生长。除了ΔuhpT - ptsI、ΔglpT - uhpT和ΔuhpT - cyaA外，所有菌株的初始细菌减少量为2 - 4 log10 cfu/mL。仅使用307mg/L可清除ΔglpT和ΔptsI突变体。
磷霉素的MIC可能不是一个好的疗效预测指标，因为可能会出现高度耐药的突变体，这取决于其他对MIC无影响的预先存在的突变。
