First-Catch, Mid-Stream and Catheterised urine: A Comparative Study of Male Urinary Microbiome by Expanded Quantitative Urine Culture and Next-Generation Sequencing
Abstract BackgroundNumerous studies have emerged in the past decade investigating human urinary microbiota. Alterations in the microbial composition of urine have been linked to structural and functional abnormalities of the lower urinary tract. There has been considerable variation in the methodology of the studies published so far including the cornerstone of any biomedical analysis: sample collection. The aim of this study was to describe the urinary microbiota of first-catch voided urine (FCU), mid-stream voided urine (MSU) and aseptically catheterised urine in men and find the most suitable approach to urine sample collection for the purpose of male urinary microbiota investigations.ResultsForty-nine men (mean age 71.3 years) undergoing endoscopic procedures in our Department of Urology were enrolled in the study. Each of them contributed three samples: first-catch urine (FCU), mid-stream urine (MSU) and a catheterised urine sample. The samples were subjected to next-generation sequencing (NGS, n=35) and expanded quantitative urine culture (EQUC, n=31). Using NGS, Bacteroidetes, Firmicutes, and Proteobacteria were the most abundant phyla in our population. The most abundant genera (in order of relative abundance) included: Prevotella, Veillonella, Streptococcus, Porphyromonas, Campylobacter, Pseudomonas, Staphylococcus, Ezakiella, Escherichia and Dialister. Eighty-two of 105 samples were dominated by a single genus. FCU, MSU and catheterised urine samples differed significantly using ANOVA in three out of five alpha-diversity measures (p<0.05): estimated number of operational taxonomic units, Chao1 and abundance-based coverage estimators. There were no differences found in Simpson and Shannon indices. Beta-diversity comparisons using the PIME method (Prevalence Interval for Microbiome Evaluation) resulted in clear clustering of urine samples according to the mode of sampling.EQUC detected cultivable bacteria in 30/31 (97%) FCU and 27/31 (87%) MSU samples. Only 4/31 (13%) of catheterised urine samples showed bacterial growth.ConclusionsUrine samples obtained by transurethral catheterisation under aseptic conditions differ from spontaneously voided urine samples and represent a better reflection of urinary bladder microbiota. Catheterised urine is the most appropriate way to sample urine in future studies of urinary bladder pathological conditions and their relation to the urinary microbiota.