Insights into antimicrobial resistance: dissemination and molecular epidemiology of carbapenemase and AmpC genes in uropathogenic Escherichia coli

This study investigated the prevalence of acquired/natural AmpC β-lactamase genes (ABLGs) and acquired carbapenemase genes (ACGs) and their association with antimicrobial resistance in uropathogenic Escherichia coli (UPEC). A total of 105 non-duplicate UPEC isolates recovered from urine specimens collected in Tehran, Iran (August 2023–January 2024), were analyzed. Antimicrobial susceptibility testing was performed by the Kirby–Bauer method. ESBL and AmpC phenotypes were determined phenotypically, and bla ACC , bla CMY , bla DHA , bla FOX , bla IMP−1 , bla IMP−2 , bla VIM−1 , and bla VIM−2 were detected by polymerase chain reaction (PCR). Resistance to ampicillin and amoxicillin was observed in all isolates, followed by ciprofloxacin (75.24%), ofloxacin (60.95%), and cefotaxime (60.95%). ESBL and AmpC phenotypes were detected in 37.14% and 11.43% of isolates, respectively. MDR, XDR, and PDR phenotypes occurred in 55.24%, 16.19%, and 2.86% of isolates. The most prevalent β-lactamase genes (BLGs) were bla IMP−2 (16.19%), bla DHA (10.48%), and bla VIM−1 (5.71%), whereas bla ACC , bla CMY and bla FOX were not detected. Most isolates (64.76%) lacked the investigated BLGs. UPEC isolates from Tehran exhibited substantial antimicrobial resistance, including MDR, XDR, and PDR phenotypes. ESBL and AmpC producers were common, with bla IMP−2 , bla DHA , and bla VIM−1 predominating. Universal ampicillin/amoxicillin resistance and marked phenotypic-genotypic diversity suggest additional resistance mechanisms.