LAUSR

INTRODUCTION AND OBJECTIVE: The microbiome of the urinary tract has a much greater association with USD than the gut microbiota, concomitant with reduced functional microbial networks. Furthermore, a diverse but consistent microbiome is often found in kidney stones regardless of composition. These data suggest that a renal microbiome (RM) both exists and is modifiable. Therefore, we aimed to determine the composition and localization of the RM and how it is impacted by antibiotic use. METHODS: We conducted a diet trial with Webster mice fed with a 1.5% oxalate diet housed in metabolic cages. Four groups and four control arms were maintained on cefazolin for 8 or 19 days, with or without 14-days recovery. Urine was collected in 3-days intervals to quantify changes to the urinary microbiome with plate cultures and metagenomic bacterial inventories. Additionally, kidneys were collected for 16s rRNA sequencing after host DNA removal, or for direct bacteria visualization in bisected kidneys with fluorescence in situ hybridization (FISH) on a confocal laser microscope using one of three FISH probes that selected for all bacteria, Lactobacilli (Lact), or Enterobacteraceae (Ent). To evaluate their specificity, all probes were first tested against pure cultures of Lactobacillus sp. and Enterobacter sp. RESULTS: Significant differences in the urinary tract microbiome were observed with long-term antibiotics relative to Lact and Ent abundance with culture based approaches (p[0.02, p[0.04, respectively). Bacterial DNA was present in all the kidney samples processed. FISH probes exhibited their expected specificity for Lact or Ent, and in kidney tissue we identified the presence of Ent (Figure 1) and Lact. Bacteria were primarily located in the renal medulla in the periphery of the loop of Henle. CONCLUSIONS: We were able to demonstrate the presence of bacteria in kidney tissue, and determine their composition and localization, through both bacterial DNA analysis and FISH staining. This has implications for the formation of kidney stones particularly because specific bacteria from the Ent family are commonly found in all types of kidney stones and in the urinary tract of stone formers while Lact in the urinary tract are anti-associated with USD.