Introduction: With the discovery of the urinary microbiome, the dogma that normal urine is sterile has been reversed. Indeed, we are only now beginning to explore how the urinary microbiome relates to various urologic maladies. Our objective was to compare the urinary microbiome between patients with simple renal cysts (SRC) and patients with a newly diagnosed, clear cell renal cell carcinoma (ccRCC) both before and after removal of the tumor. Methods: Eighteen ccRCC patients and 17 SRC patients provided an initial urine sample. Nine ccRCC patients provided a postoperative urine sample (median 159 days after surgery) and nine renal cyst patients provided a second urine sample (median 102 days after the first sample). Urine samples underwent 16S rRNA sequencing. Bacterial diversity, defined as the number of observed species (richness), relative abundance (i.e >1% of any of the ten most abundant taxa) and distribution of abundances between groups (evenness), was determined. Results: In the ccRCC group, microbial richness was decreased compared to the SRC group (22.6 vs. 33.5 bacterial species, p < 0.01). In the SRC group, there was no difference in richness between the 1st and 2nd urine sample. In the ccRCC group bacterial richness increased post-operatively (Figure 1). In the SRC group, there was increased abundance (i.e. > 1%) of Proteus, Streptococcus and Varibaculum while in the ccRCC patient group, there was an increased abundance of Anaerococcus, Corynebacterium, Enterococcus and Gardnerella (Figure 2). In the ccRCC group only, two bacteria had a >2% relative abundance: Gardnerella and Enterococcus. Conclusions: In the ccRCC group there was a markedly decreased bacterial richness, which increased post-operatively, but failed to equal the bacterial richness noted in the SRC group. Of note, Gardnerella and Enterococcus were particularly notable in the preoperative ccRCC group. SOURCE OF Funding: None.
