Fosfomycin has become a therapeutic option in urinary tract infections. Our objective was to evaluate the in vitro activity of fosfomycin against Escherichia coli isolated from urine samples in 2013, 2018 and 2021. We also determined a putative association between fosfomycin resistance and extended-spectrum β-lactamases (ESBL) production. Fosfomycin activity was evaluated against 7367, 8128 and 5072 Escherichia coli urinary isolates in 2013, 2018 and 2021, respectively. We compare the prevalence of fosfomycin-resistant strains among the ESBL- and non-ESBL-producing isolates. MICs of fosfomycin, cefotaxime, and cefotaxime-clavulanate were determined by a microdilution method. 302 ESBL-producers were selected to determine MICs of fosfomycin by agar dilution and genes encoding ESBLs were detected by PCR. Among the total of ESBL-producing strains, 14.3%, 20.8% and 20% were resistant to fosfomycin in 2013, 2018 and 2021, respectively, whereas fosfomycin resistance in non-ESBL producers was 3.5%, 4.05% and 5.53% for each year (P ≤ 0.001). In the 302 selected ESBL-producing isolates, CTX-M was the main ESBL (228 isolates), being 50.7% CTX-M-15. Resistance to fosfomycin among these ESBL-producing strains was associated (P = 0.049) with isolates that produced the CTX-M type. Our data show that fosfomycin resistance is increasing in Escherichia coli urinary isolates and it is related to ESBL-production. A follow-up of fosfomycin resistance is required.

磷霉素已成为尿路感染的治疗选择。我们的目标是评估磷霉素对2013 年、2018 年和 2021 年从尿样中分离出的大肠杆菌的体外活性。我们还确定了磷霉素抗性与超广谱 β-内酰胺酶 (ESBL) 产生之间的假定关联。磷霉素对 7367、8128 和 5072大肠杆菌的活性进行了评估分别于 2013 年、2018 年和 2021 年的尿液分离株。我们比较了产生 ESBL 和不产生 ESBL 的分离株中磷霉素耐药菌株的流行率。通过微量稀释法测定磷霉素、头孢噻肟和头孢噻肟-克拉维酸的 MIC。选择 302 个 ESBL 生产者通过琼脂稀释法测定磷霉素的 MICs，并通过 PCR 检测编码 ESBLs 的基因。2013年、2018年和2021年产ESBL菌株总数中磷霉素耐药率分别为14.3%、20.8%和20%，而非ESBL生产菌株中磷霉素耐药率分别为3.5%、4.05%和5.53%。 ( P≤0.001  )。在选定的 302 个产生 ESBL 的分离物中，CTX-M 是主要的 ESBL（228 个分离物），为 50.7% CTX-M-15。这些产生 ESBL 的菌株对磷霉素的耐药性与（P  = 0.049) 与产生 CTX-M 类型的分离株。我们的数据表明，尿中大肠杆菌对磷霉素的耐药性正在增加，并且与 ESBL 的产生有关。需要对磷霉素耐药性进行随访。