Phenotypic Fosfomycin Susceptibility and Detection of Plasmid-Mediated Resistance Genes in Clinical Uropathogenic Escherichia coli Isolates

Urinary tract infections (UTIs), predominantly caused by Escherichia coli, constitute a major global health issue due to the escalating antimicrobial resistance. This study was designed to assess the in vitro susceptibility of fosfomycin among clinical uropathogenic Escherichia coli (UPEC) isolates and to detect plasmid-mediated fosA3 and fosC2 genes in those exhibiting fosfomycin resistance. A total of 158 non-duplicated UPEC strains were collected from urine samples of patients with UTIs. Antimicrobial susceptibility of these isolates was evaluated. Phenotypic detection of extended-spectrum β-lactamases (ESBL) and carbapenemase producers in UPEC was assessed. Identification of plasmid mediated fosA3 and fosC2 genes in those exhibiting fosfomycin resistance was carried out by PCR. A total of 72% of the isolates demonstrated multidrug resistance (MDR). Extensively drug-resistant (XDR) isolates represented 15%, while PDR isolates were rare (0.6%, 1/158). ESBLs were detected in 40% of the isolates, and 31% exhibited carbapenemase production. Fosfomycin resistance was detected in 9.5% of UPEC isolates, with the fosA3 gene identified in 33% of these resistant strains, whereas fosC2 gene was not identified in any isolate. Fosfomycin demonstrated considerable in vitro activity against carbapenemase-producing, ESBL-producing, and MDR isolates with susceptibility rates of 78%, 84%, and 97%, respectively. Fosfomycin resistance among UPEC isolates is emerging but still at a relatively low level of resistance. Continuous surveillance and antimicrobial stewardship are essential to preserve fosfomycin efficacy.