[Microbial contamination of urinary calculi depending on their chemical composition]

Microbial contamination of urinary calculi and its relationship with stone composition remain insufficiently studied despite the high incidence of infectious complications of urolithiasis.

To evaluate microbial contamination of urinary calculi depending on their chemical composition and to compare the results of culture-based and molecular genetic analyses.

The study included 96 patients who underwent mini-percutaneous nephrolithotripsy. A total of 108 calculi samples were analyzed. The chemical composition was determined by polarization microscopy. Microbiological assessment included culture-based methods and 16S rRNA gene sequencing using nanopore sequencing technology.

Positive culture results were obtained in 43 (39.8%) cases. In the group of infection-related stones (carbonate apatite), microorganisms were detected in 100% of cases, whereas in metabolic stones the detection rate ranged from 26.7% to 31.7%. The most frequently identified microorganisms were Enterococcus faecalis, Streptococcus spp., Pseudomonas aeruginosa, and Klebsiella pneumoniae. Using 16S rRNA sequencing, polymicrobial communities, including anaerobic microorganisms, were identified in 18.5% of culture-negative samples.

Microbial contamination is detected in both infection-related and metabolic urinary calculi, suggesting that urinary stones may serve as a potential reservoir of microbial infection.