Assessment of Antimicrobial Resistance and Virulence of Biofilm-Forming Uropathogenic Escherichia coli from Rio de Janeiro

<b>Background/Objectives:</b> Uropathogenic <i>Escherichia coli</i> (UPEC) is the leading cause of urinary tract infections in both community and hospital settings worldwide. Antimicrobial-resistant UPEC strains pose a significant challenge for effective antibiotic therapy. In this study, 50 bacterial isolates recovered from urine samples of patients attended in different sectors of a public hospital in Rio de Janeiro over five months were analyzed to assess antimicrobial resistance and virulence profiles through broad gene screening. <b>Methods:</b> Biofilm production was assessed using a semi-quantitative adherence assay. PCR was employed to investigate 27 resistance genes, 6 virulence genes, sequence types (STs), and phylogroups. Susceptibility to 25 antimicrobial agents was determined by disk diffusion testing. Furthermore, the pathogenic potential was evaluated <i>in vivo</i> using the <i>Tenebrio molitor</i> larvae infection model. <b>Results:</b> Most UPEC isolates were moderate or strong biofilm producers (41/50; 82%). The <i>sul1</i> and <i>sul2</i> resistance genes were the most frequently detected (58%). Two virulence gene patterns were identified: <i>fyuA</i>, <i>iutA</i>, <i>fimH</i>, <i>cnf1</i> and <i>fyuA</i>, <i>iutA</i>, <i>fimH</i> (13 isolates; 26%). ST131 and ST73 were the most common sequence types (16% each), and phylogroup B2 was the most prevalent (50%). Thirty isolates (60%) were multidrug-resistant, most of which belonged to phylogroup B2. UPEC exhibited dose-dependent lethality, causing 100% mortality at 2.6 × 10⁸ CFU/mL within 24 h. <b>Conclusions:</b> These findings reinforce the urgent need for surveillance strategies and effective antimicrobial stewardship in clinical practice.