Bacteriological Analysis of Urine Cultures and Related Clinical Features in Patients with Infection Stones: A Single-Center Retrospective Cohort Analysis from Beijing, China

Objective: To compare clinical and metabolic characteristics of infection stone patients according to urine culture results and to evaluate differences among urea-splitting, non–urea-splitting , and urine culture–negative groups . Methods: A retrospective cohort study was conducted in 809 patients with infection stones, categorized as urea-splitting, non–urea-splitting , or urine culture–negative . Continuous variables were analyzed according to distribution: normally distributed data were compared using one-way ANOVA (with Bonferroni-adjusted post-hoc tests), or Welch’s ANOVA when variances were unequal; non-normally distributed data were assessed using the Kruskal–Wallis test followed by Dunn’s post-hoc test. Categorical variables were compared using Chi-square or Fisher’s exact tests with Bonferroni-adjusted pairwise comparisons when appropriate. A two-sided P < 0.05 was considered statistically significant. Results: Among 809 patients with infection stones, urine cultures were positive in 519 (64.1%), including 255 (31.5%) with urea-splitting bacteria and 264 (32.6%) with non–urea-splitting bacteria; 290 (35.8%) were culture-negative. Ureaplasma urealyticum was the most common urea-splitting organism, and Escherichia coli predominated among non–urea-splitting bacteria. Clinical features, stone characteristics, and 24-hour urine indices were similar between the urea-splitting and non–urea-splitting groups . In contrast, the urine culture-negative group had smaller stones, a higher proportion of mixed infection stones, and significantly higher 24-hour urinary potassium, calcium, phosphorus, and uric acid excretion. Conclusion: U. urealyticum was the most frequently detected urea-splitting organism in this cohort. While urea-splitting and non–urea-splitting groups showed similar clinical and metabolic profiles, the urine culture–negative group s exhibited distinct metabolic abnormalities and stone characteristics, suggesting a potentially different pathophysiologic pattern. Further studies are warranted to clarify the relationship between culture negativity and metabolic disturbances in infection stone formation. Keywords: infection stones, Ureaplasma urealyticum , urea-splitting bacteria, URINARY microbiology, host metabolic response