AUTHOR=Farizano Juan Vicente , Castagnaro Emilia , Arroyo-Egea Julián Thomas , Aparicio Juan Daniel , Vallejos Alicia Cecilia , Hebert Elvira María , Saavedra Lucila , Rapisarda Viviana Andrea , Villegas Josefina María , Grillo-Puertas Mariana TITLE=Virulence traits and bacterial interactions within the complex microbial population in urinary double-J catheters JOURNAL=Frontiers in Microbiology VOLUME=Volume 16 - 2025 YEAR=2025 URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1624743 DOI=10.3389/fmicb.2025.1624743 ISSN=1664-302X ABSTRACT=Indwelling devices, such as double-J stents, are commonly used in urological surgery and are often associated with a high risk of urinary tract infections (UTIs) due to biofilm-related complications. In this study, we characterized 27 clinical bacterial isolates from double-J catheters, including Staphylococcus spp., Enterococcus faecalis, Klebsiella pneumoniae, Escherichia coli, and Bacillus spp., to investigate their pathogenic potential. Our findings revealed that strong biofilm producers (E. coli, S. aureus, and B. subtilis) exhibited robust extracellular matrix synthesis. Notably, multidrug resistance was observed in E. coli, K. pneumoniae, and E. faecalis. Mixed-culture experiments demonstrated that Bacillus spp. enhanced the biofilm formation of uropathogens, suggesting a potential impact on clinical outcomes. The characterization of the polymicrobial population colonizing double-J catheters, as conducted in this study, is essential for understanding the complexity and clinical behavior of biofilm-related infections associated with medical devices. Additionally, our results highlight the clinical relevance of underreported genera, such as Bacillus, which are often overlooked in routine clinical diagnostics. Gaining insights into the interaction mechanisms and survival strategies of several bacterial species colonizing double-J catheters may help shift current paradigms in understanding catheter-related infections.