To investigate the distribution characteristics of bacteria in urine of patients with ureteral stent crusting.

Thirty-five patients who underwent ureteral stent placement at the Shandong Provincial Third Hospital, Shandong University Qilu Hospital, Jinan Central Hospital, and Jinan Jigang Hospital were selected from October, 2018 to March, 2019(the clinical study registration number is ChiCTR1800020025). The inclusion criteria were patients who had the stent intubated for 4 weeks after ureteroscopic lithotripsy, aged between 18 and 65 years. Exclusion criteria were patients with positive urine bacterial culture, severe gross hematuria, recent oral antibiotics, and patients with significant residual stones. This clinical study uses a cross-sectional study method, and those patients were divided into crusting group (n=23) and non-crusting group (n=12) according to the presence or absence of stent crusting. On the day of extubation, urine of the patients was collected for bacterial 16s DNA detection. The distribution characteristics of bacteria in urine of the two groups were analyzed using UPARSE, UCHIME and RDP calssifier. The total number of bacteria species, bacterial abundance and bacterial species with large-scale abundance in urine of the two groups were determined. The quantity of bacteria species and bacterial abundance in the urine between the two groups were compared, and the bacterial species with large-scale abundance in urine of the patients with stent crusting were identified.

There were no significant differences in general information such as age, body mass index, gender, affected side, type of stent tube, and stone composition between the two groups. Using 16s DNA sequencing to detect the bacteria in the urine of the two groups revealed that the number of bacterial species with abundance >1% was 11, and the number of bacterial species with abundance >0.01% was 74 in the crusting group. In the non-crusting group, the number of bacterial species with abundance >1% and >0.01% was 7 and 11, respectively. Compared with the non-crusting group, the number of bacterial species with abundance >1% in the crusting group was significantly larger ( t=5.12, P=0.000). In the crusting group, bacterial species with the top three abundance were g_Lactobacillus (23.1%), g_Bacteroides (18.8%) and g_norank_Bacteroides (17.1%). In the non-crusting group, bacterial species with the top three abundance were g_Escherichia-Shigella (32.2%), g_Enterococcus (24.9%) and g_Pseudomonas (18.2%). The three bacteria with the greatest difference between the two groups were g_ Lactobacillus (P=0.010), g_Bacteroides (P=0.004) and g_norank_Bacteroides (P=0.004), respectively.

The species and quantity of bacteria in the urine of patients with stent crusting are both significantly larger than those of patients without stent crusting. Bacteroides with larger-scale abundance in the urine of patients with stent crusting may promote the deposition of crystals on the stent wall through its structure, function and urease positive characteristics.

Urolithiasis; Bacteroides; Stents; Genetic testing; Crystallization.