Studies demonstrating bacterial DNA and cultivable bacteria in urine samples have challenged the clinical dogma that urine is sterile. Furthermore, studies now indicate that dysbiosis of the urinary microbiome is associated with pathological conditions. We propose that the urinary microbiome may influence chronic inflammation observed in the prostate, leading to prostate cancer development and progression. We therefore aimed to profile the urinary microbiome in men with positive versus negative biopsies for prostate cancer.

Urine was collected from men prior to undergoing biopsy for prostate cancer. DNA was extracted from urine pellet samples and was subjected to bacterial 16S rDNA Illumina sequencing and 16S rDNA quantitative PCR. We determined the association between bacterial species and the presence or absence of cancer, cancer grade, and type and degree of prostate inflammation.

Urine samples showed the presence of diverse bacterial populations. There were no significant differences in alpha or beta diversity and no clear hierarchical clustering of benign or cancer samples. We identified a cluster of pro-inflammatory bacteria previously implicated in urogenital infections in a subset of samples. Many species, including known uropathogens, were significantly differentially abundant among cancer and benign samples, in low versus higher grade cancers, and in relation to type and degree of prostate inflammation.

We report the most comprehensive study to date of the male urinary microbiome and its relationship to prostate cancer. Our results suggest a prevalence of pro-inflammatory bacteria and uropathogens in the urinary tract of men with prostate cancer.