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

Xijie Ding,1,2 Zhichao Chi,2 Jianxing Li,2 Guojun Chen,1 Chaoyue Ji,2 Weiguo Hu2 1Department of Urology, Qinghai University Affiliated Hospital, School of Clinical Medicine, Qinghai University, Xining, 810000, People’s Republic of China; 2Department of Urology, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua Medicine, Tsinghua University, Beijing, 102218, People’s Republic of ChinaCorrespondence: Weiguo Hu, Department of Urology, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua University, No. 168, Litang Road, Changping District, Beijing, 102218, People’s Republic of China, Email [email protected]: 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 groups 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