Urinary microbiota and bacterial membrane vesicles in chronic kidney disease: contribution to antimicrobial-resistant...

Chronic kidney disease (CKD) is associated with an increased risk of severe urinary tract infections (UTIs), particularly those caused by antimicrobial-resistant bacteria. Although urinary microbiota and bacterial membrane vesicles (BMVs) are thought to contribute to UTI pathogenesis, their roles in CKD remain insufficiently understood. In this exploratory study, urine samples were collected from 10 male patients with CKD (eGFR <45 mL/min/1.73 m²) and 10 male non-CKD controls (eGFR ≥60 mL/min/1.73 m²). Urinary microbiota and BMV fractions were isolated and analyzed to compare microbial composition and antimicrobial resistance gene (ARG) profiles, and to evaluate their potential involvement in UTI development and the emergence of antimicrobial resistance in CKD. Both fractions were subjected to shotgun metagenomic sequencing; metagenomic analysis of BMVs was performed using pooled samples within each group. In addition, BMV fractions were characterized by transmission electron microscopy and 16S rRNA gene PCR. Urinary microbiota α-diversity was significantly lower in patients with CKD than in controls (ACE index, p = 0.04). Vesicle-like structures consistent with BMVs, with diameters of 20-200 nm, were detected in urine samples from both controls and patients with CKD. Principal coordinate analysis demonstrated that BMV fractions clustered within the corresponding urinary microbiota profiles. Furthermore, multiple antimicrobial resistance genes (ARGs), including ftsI and adeF, were identified in both urinary microbiota and BMV fractions. This study provides exploratory evidence of reduced urinary microbiota α-diversity in patients with CKD and the presence of ARGs in both urinary microbiota and BMV fractions from controls and patients with CKD. These findings suggest microbiological factors that may contribute to the high incidence of antimicrobial-resistant UTIs in this population. Future validation in larger cohorts with individual-level BMV profiling will be required to determine whether analyses focusing on urinary microbiota and BMVs can contribute to a better understanding of antimicrobial-resistant UTIs and to improved infection risk assessment in patients with CKD.