Gil-Gil Teresa, Martínez José Luis
Centro Nacional de Biotecnología, CSIC, Madrid, Spain.
Programa de Doctorado en Biociencias Moleculares, Universidad Autónoma de Madri, Madrid, Spain.
Front Microbiol. 2022 May 10;13:863635. doi: 10.3389/fmicb.2022.863635. eCollection 2022.
It is generally accepted that fosfomycin activity is higher in the presence of glucose-6-phosphate, since its inducible transporter UhpT is one of the gates for fosfomycin entry. Accordingly, fosfomycin susceptibility tests are performed in the presence of this sugar; however, since lacks UhpT, it is doubtful that glucose-6-phosphate might be a fosfomycin adjuvant in this microorganism. The aim of the work was to determine whether glucose-6-phosphate or other metabolites may alter the activity of fosfomycin against . To that goal, checkerboard assays were performed to analyze the synergy and antagonism of compounds, such as glucose-6-phosphate, fructose, phosphoenolpyruvate, and glyceraldehyde-3-phosphate, among others, with fosfomycin. Besides, minimal inhibitory concentrations of fosfomycin against a set of clinical isolates presenting different levels of expression of the SmeDEF efflux pump were determined in the presence and absence of said compounds. Finally, intracellular fosfomycin concentrations were determined using a bioassay. Our results show that, opposite to what has been described for other bacteria, glucose-6-phosphate does not increase fosfomycin activity against ; it is a fosfomycin antagonist. However, other metabolites such as fructose, phosphoenolpyruvate and glyceraldehyde-3-phosphate, increase fosfomycin activity. Consistent with these results, glucose-6-phosphate decreases fosfomycin internalization (a feature against current ideas in the field), while the other three compounds increase the intracellular concentration of this antibiotic. These results support that current standard fosfomycin susceptibility tests made in the presence of glucose-6-phosphate do not account for the actual susceptibility to this antibiotic of some bacteria, such as . Finally, the innocuous metabolites that increase susceptibility to fosfomycin found in this work are potential adjuvants, which might be included in fosfomycin formulations used for treating infections by this resistant pathogen.
一般认为，在6-磷酸葡萄糖存在的情况下，磷霉素活性更高，因为其诱导型转运蛋白UhpT是磷霉素进入的通道之一。因此，磷霉素药敏试验是在这种糖存在的情况下进行的；然而，由于[某种微生物]缺乏UhpT，6-磷酸葡萄糖是否可能是这种微生物中的磷霉素佐剂值得怀疑。这项工作的目的是确定6-磷酸葡萄糖或其他代谢物是否会改变磷霉素对[某种微生物]的活性。为了实现这一目标，进行了棋盘法试验，以分析6-磷酸葡萄糖、果糖、磷酸烯醇丙酮酸和3-磷酸甘油醛等化合物与磷霉素之间的协同作用和拮抗作用。此外，在有和没有上述化合物的情况下，测定了磷霉素对一组呈现不同水平SmeDEF外排泵表达的临床[某种微生物]分离株的最低抑菌浓度。最后，使用生物测定法测定细胞内磷霉素浓度。我们的结果表明，与其他细菌的情况相反，6-磷酸葡萄糖不会增加磷霉素对[某种微生物]的活性；它是磷霉素的拮抗剂。然而，其他代谢物如果糖、磷酸烯醇丙酮酸和3-磷酸甘油醛会增加磷霉素的活性。与这些结果一致，6-磷酸葡萄糖会降低磷霉素的内化（这一特征与该领域的当前观点相反），而其他三种化合物会增加这种抗生素的细胞内浓度。这些结果支持，目前在6-磷酸葡萄糖存在下进行的标准磷霉素药敏试验不能反映某些细菌如[某种微生物]对这种抗生素的实际敏感性。最后，在这项工作中发现的增加[某种微生物]对磷霉素敏感性的无害代谢物是潜在的佐剂，可能会被纳入用于治疗这种耐药病原体感染的磷霉素制剂中。
