Phylogenetic Diversity, Biofilm Production, and Antibiotic Resistance Profiling of Uropathogenic <i>Escherichia coli</i> Isolated from Children with Vesicoureteral Reflux: Complicating Factors for Treatment and Recurrent Urinary Tract Infections

<b><i>Introduction:</i></b> Uropathogenic <i>Escherichia coli</i> (UPEC) are the most common cause of urinary tract infections (UTI). This study investigated the genetic relatedness, biofilm-forming capacity, and antimicrobial resistance profiles in the extended-spectrum beta-lactamase (ESBL)-producing UPEC collected from children with vesicoureteral reflux (VUR) suffering from UTI. <b><i>Materials and Methods:</i></b> In this cross-sectional investigation, a total of 80 nonduplicated UPEC isolates were collected from children afflicted with VUR. Antimicrobial susceptibility testing and phenotypic production of ESBL were conducted according to the Clinical and Laboratory Standards Institute (2023) recommendations. Furthermore, PCR tests were used to detect the presence of ESBL genes. Biofilm formation in 96-well microtiter plates was assessed. Finally, the clonal diversity of the isolates was examined using the Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR. <b><i>Results:</i></b> Out of all collected isolates, 71.2% (<i>n</i> = 57/80) were ESBL producers and 31.2% (<i>n</i> = 25/80) were multidrug resistant (MDR). The frequency of the <i>bla_CTX-M</i> gene was 65.0% and 77.5% of the isolates were biofilm producers. ESBL-producing UPEC isolates were clustered by the ERIC-PCR method into the nine groups labeled A-I. <b><i>Conclusion:</i></b> Our findings indicate a high and rising prevalence of MDR and ESBL-producing UPEC among children with VUR. This underscores the urgent need for appropriate empirical antibiotic selection, routine monitoring of resistance patterns, and long-term prophylactic strategies to reduce recurrence and improve clinical management in this vulnerable population.