Purpose: The dogma that urine is sterile has been overturned and dysbiosis of the urinary microbiome has been linked to many urological disorders. We tested the hypothesis that the urinary microbial composition may be different between men with or without bladder cancer in catheter collected urines, bladder washouts and midstream voided urines, and may be dependent on tumor staging.
Materials and methods: Liquid samples were collected from male patients with bladder cancer, and sex and age matched nonneoplastic controls. Total DNA was extracted and processed for 16S rRNA gene sequencing. Bioinformatic analysis for microbial classification was performed to assess diversity and variations.
Results: The urinary microbiome associated with catheter collected urine samples of patients with bladder cancer was characterized by a significantly increased abundance of Veillonella (p=0.04) and Corynebacterium (p=0.03), and decreased Ruminococcus (p=0.03) compared to controls, with differences exacerbating with disease progression. Compared to catheterized urines, bladder cancer washouts showed the specific increase of some taxa, like Burkholderiaceae (p=0.014), whereas midstream urines were enriched in Streptococcus (p <0.0001), Enterococcus (p <0.0001), Corynebacterium (p=0.038) and Fusobacterium (p <0.0001).
Conclusions: The bladder is colonized by endogenous bacteria and microbial modifications characterize the microbiome of patients with bladder cancer. Different microbial compositions can be characterized by changing sampling strategy. These results pave the way for exploring new diagnostic and therapeutic options based on the manipulation of the bacterial community.
Keywords: microbiota; tumor microenvironment; urinary bladder neoplasms.