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

Abstract

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

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

Materials and methods: 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.

Results: 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.

Conclusion: 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.