Evidence of Uncultivated Bacteria in the Adult Female Bladder

Abstract

c Clinical urine specimens are usually considered to be sterile when they do not yield uropathogens using standard clinical cultivation procedures. Our aim was to test if the adult female bladder might contain bacteria that are not identified by these routine procedures. An additional aim was to identify and recommend the appropriate urine collection method for the study of bacterial communities in the female bladder. Consenting participants who were free of known urinary tract infection provided urine samples by voided, transurethral, and/or suprapubic collection methods. The presence of bacteria in these samples was assessed by bacterial culture, light microscopy, and 16S rRNA gene sequencing. Bacteria that are not or cannot be routinely cultivated (hereinafter called uncultivated bacteria) were common in voided urine, urine collected by transurethral catheter (TUC), and urine collected by suprapubic aspirate (SPA), regardless of whether the subjects had urinary symptoms. Voided urine samples contained mixtures of urinary and genital tract bacteria. Communities identified in parallel urine samples collected by TUC and SPA were similar. Uncultivated bacteria are clearly present in the bladders of some women. It remains unclear if these bacteria are viable and/or if their presence is relevant to idiopathic urinary tract conditions. C ulture-dependent methods are typically used to test if clinical urine specimens contain uropathogens, and the results play a pivotal role in the diagnosis and treatment of urinary tract infection symptoms in women. Clinical urine cultures are considered positive when the colony count of a recognized uropathogen, such as Escherichia coli, Pseudomonas, Klebsiella, or group B Streptococcus reaches a predefined threshold (14). Bacterial urinary tract infections (UTI) caused by these typical uropathogens elicit symptoms that typically improve or resolve in response to appropriate antibiotic therapy. For other common urinary disorders, including overactive bladder, urinary incontinence, and a spectrum of pain disorders, e.g., painful bladder syndrome and interstitial cystitis, the clinical urine culture is negative and antibiotics are not given for clinical treatment. Under these conditions, the etiology is unknown, and research into these conditions so far has not incorporated culture-independent assessments of bladder infection, such as bacterial 16S rRNA PCR and metagenomic sequencing approaches.Recently, a concerted international effort, known as the Human Microbiome Project (http://commonfund.nih.gov/hmp/), has begun to catalogue the core microbial composition of the healthy human body in order to determine if changes to the core microbial communities affect health. Sequence analysis of 16S rRNA, the workhorse of that effort, has been used to determine the microflora composition of healthy skin (12, 13), the gastrointestinal tract (7, 9, 36), the mouth (24, 25, 28), and the vagina (11,16,27,39) and to correlate certain diseases with changes in this composition (9,11,27). A common the...

Urinary Bacteria in Adult Women With Urgency Urinary Incontinence

“…These culture-independent techniques hold great promise in advancing our ability to detect and study urinary bacteria. Such techniques have already shown that urine from asymptomatic women is often not "sterile" [3,20] and that voided urine of adult males contains diverse bacteria. In both cases, many of the bacteria identified cannot be or are not routinely cultivated by clinical microbiology laboratories [20].…”

“…Studies based on DNA and culture have provided evidence of live bacteria in urine samples that are deemed "culture-negative" by standard clinical microbiological procedures [3,5].…”

“…Recent DNA and culture-based evidence suggests that even when urine cultures are negative, detectable bacterial communities (microbiota) exist in the urine of some adult women, regardless of their urinary symptoms [3][4][5][6]. In addition to broader implications of this discovery for a variety of lower urinary tract disorders, these findings may allow us to identify baseline factors that predispose or even protect women to subsequent UTI.…”

The Clinical Urine Culture: Enhanced Techniques Improve Detection of Clinically Relevant Microorganisms

“…Given emerging evidence that documents the presence of urinary microbiota in many adult women (7)(8)(9)(10)(11)(12)(13)(14)(15), it is clear that the mere presence of an organism should not prompt antibiotic treatment. However, clinicians are likely to benefit from a more complete report of organisms present within a symptomatic patient's urine.…”

Commentary: Complicated Urinary Tract Infections: What's a Lab To Do?

“…Normal urine was assumed to be sterile, and patients diagnosed with UTIs had urine with bacterial counts of Ͼ10 5 CFU/ml. While this is still common practice today, Stamm et al reported documented UTIs in women with colony counts between 10 2 and 10 5 in 1982 (2), and more recently, the interpretation of urine culture results has been further complicated by reports that urine is not necessarily sterile (3,4). Moreover, diagnosis is even further complicated by the fact that urine samples are often contaminated with normal indigenous bacteria during the collection process.…”