Lower urinary tract symptom (LUTS) severity in men is associated with detectable bacteria in urine obtained via catheter, according to a new study that investigators say demonstrated for the first time that collection of catheterized urine is the most appropriate way to sample male bladder microbiota.

Petar Bajic, MD, of Loyola University Medical Center in Maywood, Illinois, and colleagues studied 28 men undergoing surgery for benign prostatic enlargement (BPE)/LUTS and 21 undergoing non-BPE/LUTS surgery. They stratified men by International Prostate Symptom Score (IPSS). Paired voided/catheterized urine specimens were collected for expected quantitative urine culture (EQUC) and 16S ribosomal RNA gene sequencing.

Lower urinary tract microbiota (LUTM) were detected in catheterized urine of 22.2% of men with mild LUTS, 305 of those with moderate LUTS, and 57.1% of those with severe LUTS, the investigators reported online ahead of print in European Urology Focus.

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Bacteria were present in the catheterized urine of 19 men. Of these, 4 men (21.1%) were in IPSS categories less than 8, 3 (15.7%) were in categories 8–19, and 12 (63.2%) in categories greater than 19. Increased IPSS category was associated with significant 2.2-fold higher odds of detectable bacteria in catheterized urine.

Nearly all voided urine specimens showed detectable bacteria, so investigators found no association between bacteria in voided urine and increasing IPSS.

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“For the first time, we have successfully applied EQUC and 16S sequencing to male catheterized urine and associated the presence of bacteria with increasing IPSS,” the authors wrote.

Many patients with detectable microbiota in both voided and catheterized urine showed unique organisms in their voided samples. “This indicates that most voided urine microbiota is sampled from the urinary tract distal to the bladder and that the male bladder is a relatively low-biomass environment,” they stated. “This observation confirms for the first time that collection of catheterized urine is the most appropriate method of sampling male bladder microbiota.”

Men in the BPE/LUTS surgery group was significantly older than those in the non-BPE/LUTS surgery group (mean 64.3 vs 56 years), and they had a higher proportion of patients with hypertension (64.3% vs 23.8%).

In a discussion of study limitations, the authors noted that the patients undergoing BPE/LUTS surgery and non-BPE/LUTS surgery were not matched with respect to age or hypertension. “As BPE/LUTS is a disease of the elderly, most patients with mild LUTS were younger overall,” they wrote. “The difference in hypertension is likely attributable to the difference in age alone.”

Dr Bajic and colleagues pointed out, however, that patients with and without identifiable microbiota in their bladders had no differences with respect to any baseline characteristics.


Bajic P, Van Kuiken ME, Burge BK et al. Male bladder microbiome relates to lower urinary tract symptoms. Eur Urol Focus. 2018; published online ahead of print.