Male Bladder Microbiome Relates to Lower Urinary Tract Symptoms

In women, compelling evidence associates lower urinary tract microbiota (LUTM) with lower urinary tract symptoms (LUTS); a similar association in men with benign prostate enlargement (BPE) is not established.

To determine whether associations exist between LUTM and LUTS.

Forty-nine male volunteers, aged 40-85 yr, were recruited from one academic tertiary care center. Twenty-eight patients undergoing BPE/LUTS surgery and 21 undergoing non-BPE/LUTS surgery were stratified by International Prostate Symptom Score (IPSS), and paired voided/catheterized urine specimens were collected for expanded quantitative urine culture (EQUC) and 16S ribosomal RNA gene sequencing.

Primary and secondary outcomes were presence of detectable LUTM and specific bacterial members of the LUTM, respectively. Baseline data were compared. Univariable logistic regression models were used to calculate odds ratios (ORs) for IPSS category associated with the presence of bladder microbiota. Relative LUTM proportions were compared with IPSS using chi-square tests.

Thirty-nine percent of catheterized and 98% of voided specimens contained LUTM. Catheterized and voided LUTM differed significantly. LUTM was detected in catheterized urine of 22.2% of men with mild LUTS, 30.0% with moderate LUTS, and 57.1% with severe LUTS (p=0.024). Increased IPSS category was associated with significantly higher odds of detectable bacteria (OR: 2.21, 95% confidence interval: 1.09-4.49). Small sample size limited this study, making it unable to identify significant differences in specific bacterial taxa based on IPSS.

Voided urine does not adequately characterize the male bladder microbiome. In males with and without BPE, IPSS severity was associated with detectable bacteria in catheterized urine, which samples the bladder. Additional studies are needed to identify specific bladder bacteria associated with LUTS.

To study bladder bacteria, urine should be collected with a catheter. Men with severe urinary symptoms are more likely to have detectable bladder bacteria than those with less severe symptoms.