Detection of biofilms on explanted urinary incontinence slings and their relationship with pain, exposure, or urinary tract complications.

UNLABELLED: Midurethral slings (MUS) are synthetic mesh implants used to treat stress urinary incontinence in women. Positioned via retropubic or transobturator approaches, they support the mid-urethra to maintain closure during increases in intra-abdominal pressure. Although generally effective, long-term MUS complications have been associated with chronic inflammation, pain, and infection, with explanted slings often showing bacterial colonization. The underlying mechanisms remain unclear, particularly the role of microbial biofilms. We examined the presence and characteristics of biofilms on MUS removed for various complications to better inform clinical management. MUS samples (n = 112) from 52 women were imaged using confocal laser scanning microscopy following application of a eubacterial FISH probe, TOTO-1, and DAPI. Biofilms were detected on all samples, forming dense bacterial aggregates along mesh fibers. The vaginal portions of the MUS demonstrated higher biofilm volumes than retropubic or obturator regions. However, mesh exposed through vaginal tissue did not show increased bacterial load. When all samples were analyzed, no significant differences in biofilm volume were observed between complication types, including chronic pain, vaginal or lower urinary tract perforation, and recurrent incontinence. While biofilms were universally present, greater volumes in the vaginal region did not correlate with worse clinical outcomes. These findings suggest a threshold between benign colonization and clinically significant infection. Variation in bacterial composition, rather than biofilm quantity, may influence host response and the development of mesh-related complications. IMPORTANCE: Biofilms are common on explanted midurethral slings, but their volume does not predict complications. These findings suggest that bacterial composition and host response, rather than bacterial load, drive mesh-related morbidity. Understanding these factors may improve mesh design and guide strategies to prevent infection and chronic complications.