Abstract / Summary
Abstract Objectives This study included patients undergoing percutaneous nephrolithotomy (PCNL) for calcium oxalate or infection stones whose preoperative midstream urine cultures yielded only uropathogen taxa generally classified as non-urease-producing. We compared the distribution of cultured taxa between the two stone groups and explored clinical factors associated with the detection of Escherichia coli , Enterococcus spp., and Pseudomonas aeruginosa in separate analyses. Methods This single-center retrospective cohort study screened patients who underwent PCNL at Beijing Tsinghua Changgung Hospital between January 2016 and December 2020. After application of the prespecified eligibility criteria, 343 patients with kidney stones and preoperative midstream urine cultures positive for uropathogen taxa generally classified as non-urease-producing were included in the final analysis. Stone composition was determined by Fourier-transform infrared spectroscopy. Infection stones were defined as stones containing ≥ 50% struvite, with or without carbonate apatite; calcium oxalate stones were defined as stones containing a combined proportion of ≥ 50% calcium oxalate monohydrate and calcium oxalate dihydrate. Logistic regression models were fitted separately to explore factors associated with the detection of Escherichia coli , Enterococcus spp., and Pseudomonas aeruginosa . The three taxa were also analyzed together in a secondary exploratory analysis, with other taxa as the reference. Results Among the 343 patients, the overall distribution of cultured taxa differed between patients with infection stones and those with calcium oxalate stones ( P = 0.002). Taxon-specific analyses yielded different estimates across the three taxa. For infection stones, the aOR was 4.416 (95% CI, 1.614–12.086) for Pseudomonas aeruginosa , compared with 1.337 (95% CI, 0.816–2.191) for Escherichia coli and 0.901 (95% CI, 0.508–1.596) for Enterococcus spp. Female sex was associated with higher relative odds of Escherichia coli detection and lower relative odds of Enterococcus spp. and Pseudomonas aeruginosa detection. In the secondary combined analysis, infection stones were associated with higher odds of detecting one of the three taxa (aOR = 2.047, 95% CI, 1.100–3.807), but this association was attenuated when all candidate variables were entered simultaneously (aOR = 1.792, 95% CI, 0.870–3.691). Overall, the associations with stone composition and sex differed across the three taxa. Conclusions Among patients undergoing PCNL whose preoperative midstream urine cultures were positive for uropathogen taxa generally classified as non-urease-producing, the distribution of cultured taxa differed between infection stones and calcium oxalate stones. Taxon-specific analyses indicated higher relative odds of Pseudomonas aeruginosa detection among patients with infection stones. Stone composition may help clinicians interpret an already positive preoperative culture but cannot replace pathogen identification or antimicrobial susceptibility testing. Clinical trial number Not applicable.