Urinary tract infections (UTIs) caused by Escherichia coli represent a significant public health concern due to the high virulence and antimicrobial resistance exhibited by these pathogens. This study aimed to analyze the phylogenetic diversity and antibiotic resistance profiles of Uropathogenic E. coli (UPEC) strains isolated from UTI patients in Algeria, focusing on virulence factors such as extended β-lactamase (ESBL) production, biofilm formation, and hemolytic activity. Phylogenetic grouping of 86 clinical imipenem resistant E. coli isolates showed the prevalence of group B2 (48.9%), followed by groups E (22.1%), unknown (12.8%), A (8.1%), and B1 (4.7%), and Clade I, D, Clade I, or Clade II (1.2%). The highest resistance rates were observed towards amoxicillin (86.04%), ticarcillin (82.55%), piperacillin (73.25%), nitrofurantoin (84.88%), and trimethoprim-sulfamethoxazole (51.16%). Notably, 69.8% of UPEC strains were multidrug-resistant (MDR) and 23.2% were extensively drug-resistant (XDR). Additionally, 48.9%, 42%, and 71% of strains demonstrated ESBL production, hemolytic activity, and weak biofilm production, respectively. Continuous monitoring and characterization of UPEC strains are essential to track the spread of the most resistant and virulent phylogenetic groups over time, facilitating rapid therapeutic decisions to treat infections and prevent the emergence of new resistant organisms, helping choose the most effective antibiotics and reducing treatment failure.

Background. Antibiotic resistance is a growing global health challenge, complicating the management of infections. Aminoglycosides are increasingly associated with resistance, raising the risk of clinical complications and mortality in severe infections. This study aimed to characterize the epidemiological profile of 135 aminoglycoside-resistant clinical strains collected in Setif between 2021 and 2023. Methods. Antibiotic susceptibility testing was performed according to EUCAST guidelines, and phenotypic assays were conducted to assess key virulence traits, including biofilm formation and enzyme production. Results. Aminoglycoside resistance was more frequently observed in female patients (55.6%) and was found to be predominant among adults (68.1%). Urinary tract infections represented the main clinical presentation (76.3%), with Escherichia coli being the most common isolate (40.7%). High resistance rates were detected for amoxicillin (83%), amoxicillin–clavulanic acid (80%), cephalexin (74.8%), cefixime (71.1%), trimethoprim–sulfamethoxazole (74.8%), and gentamicin (72.6%). Conversely, chloramphenicol (53.3%), imipenem (47.4%), amikacin (47.4%), and piperacillin–tazobactam (31.1%) remained comparatively more effective. Multidrug resistance involving seven antibiotics occurred in 25.6% of isolates, with notable cross-resistance patterns between gentamicin and β-lactam antibiotics (5 out of 22). Genotypic analysis showed that 43% of isolates carried at least one β-lactamase gene, whereas 9.6% harbored a qnr determinant. Regarding virulence factors, isolates with low biofilm-forming ability were found to be the most common (62.96%). Conclusion. In conclusion, this study revealed substantial variations in aminoglycoside resistance in Setif, shaped by demographic, clinical, and bacteriological factors.