Urinary Microbiome Dysbiosis in Children With Congenital Uropathies at Varying Risk for Urinary Tract Infections

Febrile urinary tract infections (UTIs) may occur in 30% to 50% of children with vesicoureteral reflux (VUR) or posterior urethral valves (PUVs), frequently leading to renal scarring despite chemoprophylaxis. Approximately 15% of children with uretero-pelvic junction obstruction (UPJO) may develop UTIs. However, investigations that can identify at-risk children before the first episode of UTI are lacking. In this exploratory study, we investigated the preinfection urinary microbiome in Indian children with congenital anomalies of the kidney and urinary tract (CAKUT) to determine whether microbiome alterations, metabolic potential, and antibiotic resistance profiles precede UTI.

In this prospective cohort study with follow-up, urine samples were collected from 80 children: 36 with newly diagnosed, antibiotic-naïve CAKUT (18 UPJO, 12 VUR, 6 PUV) and 44 controls. Patients were stratified a priori into low (n = 19) and high-risk (n = 17) groups using clinically defined UTI-susceptibility criteria. V3-V4 16S ribosomal RNA sequencing was used to define urinary microbial profiles. Alpha- and beta-diversity were compared using Shannon index and permutational multivariate analysis of variance (PERMANOVA), respectively. Sliding-window and network-based analyses were used to map dysbiosis gradients. Patients were followed-up longitudinally to assess UTI incidence. Identified dysbiosis-linked microbial markers at baseline were investigated using Kaplan-Meier and Cox-proportional hazard-based analyses as predictors of UTI-risk. Metabolic functions were inferred from taxonomic data. Antibiotic resistance patterns were characterized using the Comprehensive Antibiotic Resistance Database - Resistance Gene Identifier (CARD-RGI) and the World Health Organization Access, Watch, and Reserve classification.

Urinary microbial alpha diversity declined significantly from controls to low-risk to high-risk groups (P = 0.002), accompanied by an increase in intragroup variability (P ≤ 0.005). PERMANOVA revealed distinct clustering by risk (R ² = 0.11; P = 0.001). Dysbiosis scores inversely correlated with the first Kendall Principal Coordinates Analysis (PCoA) axis (ρ = -0.62; P < 0.001). With increasing risk of UTI, the commensal, control-associated genera declined along this axis while the facultative pathogens became dominant. Control-associated microbiomes favored short- and branched-chain fatty acid and spermidine production; high-risk microbiomes overproduced ammonia, putrescine, and cadaverine. Resistance to 18 of 22 routinely tested antibiotics was almost confined to the 31 risk-associated microbiomes (P = 0.001). During the median (interquartile range) follow-up of 564 (518-594) months, 14 of 36 children with CAKUT developed UTIs, and baseline depletion of health-associated microbial consortia correlated with reduced UTI-free survival. A panel of 10 species-level and 12 genus-level taxa were identified as health-associated markers negatively associated with future UTI-risk during follow-up investigation.

Children with CAKUT exhibit urinary microbiome dysbiosis before their first symptomatic UTI, characterized by loss of conserved health-associated taxa, metabolic imbalance, and broad-spectrum antibiotic resistance. These findings support the potential of microbiome-informed, noninvasive risk stratification and microbiome-tailored prophylaxis, while establishing the first Indian pediatric reference set for CAKUT-related UTI prevention.