Martín-Gutiérrez Guillermo, Docobo-Pérez Fernando, Rodríguez-Martínez Jose Manuel, Pascual Alvaro, Blázquez Jesús, Rodriguez-Beltrán Jeronimo
Unidad de Enfermedades Infecciosas, Microbiología y Medicina Preventiva, Hospital Universitario Virgen del Rocio, 41013 Seville, Spain.
Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013 Seville, Spain.
Antibiotics (Basel). 2020 Nov 12;9(11):802. doi: 10.3390/antibiotics9110802.
Mutations that confer low-level fosfomycin resistance (LLFR) but not clinical resistance in are increasingly reported. LLFR strains can become clinically resistant under urinary tract physiological conditions or may act as gateways for highly resistant subpopulations by the selection of additional LLFR mutations. Nevertheless, most LLFR strains are impossible to detect under routine fosfomycin susceptibility determinations. Here, we have explored the possibility of detecting LLFR variants by reducing glucose-6-phosphate (G6P) concentration in fosfomycin susceptibility testing for strains. As a proof of concept, fosfomycin minimal inhibitory concentrations (MICs) and disk diffusion susceptibility tests were performed for strain BW25113 and 10 isogenic derivatives carrying the most prevalent LLFR chromosomal mutations (∆, ∆, ∆, and ∆) and their double combinations. Whereas standard G6P concentrations detected only ∆ single and double variants, assays with reduced G6P detected all LLFR variants. In addition, G6P levels were determined to be ≤5 µg/mL in urine samples from 30 patients with urinary tract infection (UTI) caused by and 10 healthy volunteers, suggesting that most bacterial cells in uncomplicated UTIs are facing fosfomycin under low G6P concentration. Reducing G6P allows for the detection of LLFR variants, which may suppose a risk for future resistance development, especially in UTIs.
越来越多的报道称，在大肠杆菌中存在一些赋予低水平磷霉素抗性（LLFR）但不具备临床抗性的突变。LLFR菌株在尿路生理条件下可能会变成临床抗性菌株，或者通过选择额外的LLFR突变，可能成为高抗性亚群的通道。然而，在常规磷霉素敏感性测定中，大多数LLFR菌株无法被检测到。在此，我们探讨了通过降低磷霉素敏感性试验中葡萄糖-6-磷酸（G6P）的浓度来检测大肠杆菌LLFR变异体的可能性。作为概念验证，我们对携带最常见的LLFR染色体突变（∆、∆、∆和∆）及其双重组合的大肠杆菌菌株BW25113和10个同基因衍生物进行了磷霉素最低抑菌浓度（MIC）和纸片扩散敏感性试验。标准G6P浓度仅能检测到∆单突变和双突变变体，而降低G6P浓度的试验能检测到所有LLFR变体。此外，在30例由大肠杆菌引起的尿路感染（UTI）患者和10名健康志愿者的尿液样本中，G6P水平被测定为≤5μg/mL，这表明在单纯性UTI中，大多数细菌细胞面临的是低G6P浓度下的磷霉素。降低G6P浓度能够检测到LLFR变体，这可能对未来的耐药性发展构成风险，尤其是在UTI中。
