The Role of the Genitourinary Microbiome in Pediatric Urology: a Review

Urinary Microbiota of Healthy Prepubescent Girls and Boys-A Pilot Study

BACKGROUND

The urinary microbiota of healthy children has rarely been studied, and potential differences between boys and girls have not been addressed. Thus, this study aimed to compare the urinary microbiota of healthy prepubescent girls and boys.

METHODS

We included healthy children aged between 4 and 10 years who were free of functional or organic urinary tract diseases and had no history of urinary tract infection. We collected the mean portion of morning urine during natural micturition and determined aerobic and anaerobic microbiota using HiCrome™ chromogenic growth media. We identified microorganisms on the basis of morphotinctural properties and analyzed α- and β-diversity of microorganisms isolated from the urine of boys and girls.

RESULTS

Mean age of the children was 6.1 ± 3.2 years. In general, four-component (28.1%) as well as two-component (15.6%), three-component (15.6%), and six-component (12.5%) combinations of microorganisms prevailed in the urine of children. The urine of boys exhibited four-component combinations significantly more often than that of girls (p ˂ 0.05), while the urine of girls contained seven-component microbial combinations significantly more often than that of boys (p ˂ 0.05). Comparison of multicomponent combinations of microorganisms in boys and girls revealed an overrepresentation of Enterococcus spp. in girls (p < 0.05). Furthermore, there was a trend towards higher microbial α-diversity in the urine of girls, but the difference between girls and boys was not significant.

CONCLUSIONS

The urine of healthy prepubescent children contained various aerobic-anaerobic combinations of microorganisms. Their diversity in the urine of girls and boys did not differ significantly. However, the level of α-diversity of microorganisms was higher in girls than in boys. We noted differences in the prevalence of certain taxa of microorganisms in the urine of boys and girls. Our study showed a close functional relationship between aerobic and anaerobic microorganisms detected in the urine of children in more than half of the cases.

Current and emerging strategies to curb antibiotic-resistant urinary tract infections

Rising rates of antibiotic resistance in uropathogenic bacteria compromise patient outcomes and prolong hospital stays. Consequently, new strategies are needed to prevent and control the spread of antibiotic resistance in uropathogenic bacteria. Over the past two decades, sizeable clinical efforts and research advances have changed urinary tract infection (UTI) treatment and prevention strategies to conserve antibiotic use. The emergence of antimicrobial stewardship, policies from national societies, and the development of new antimicrobials have shaped modern UTI practices. Future UTI management practices could be driven by the evolution of antimicrobial stewardship, improved and readily available diagnostics, and an improved understanding of how the microbiome affects UTI. Forthcoming UTI treatment and prevention strategies could employ novel bactericidal compounds, combinations of new and classic antimicrobials that enhance bacterial killing, medications that prevent bacterial attachment to uroepithelial cells, repurposing drugs, and vaccines to curtail the rising rates of antibiotic resistance in uropathogenic bacteria and improve outcomes in people with UTI.

Epigenetic insights to pediatric uropathology: Celebrating the fundamental biology vision of Tony Khoury

INTRODUCTION

Many pediatric urology conditions affect putatively normal tissues or appear too commonly to be based solely on specific DNA mutations. Understanding epigenetic mechanisms in pediatric urology, therefore, has many implications that can impact cell and tissue responses to settings, such as environmental and hormonal influences on urethral development, uropathogenic infections, obstructive stimuli, all of which originate externally or extracellularly. Indeed, the cell's response to external stimuli is often mediated epigenetically. In this commentary, we highlight work on the critical role that epigenetic machinery, such as DNA methyltransferases (DNMTs), Enhancer of Zeste Polycomb Repressive Complex 2 Subunit (EZH2), and others play in regulating gene expression and cellular functions in three urological contexts.

DESIGN

Animal and cellular constructs were used to model clinical pediatric uropathology. The hypertrophy, trabeculation, and fibrosis of the chronically obstructed bladder was explored using smooth muscle cell models employing disorganised vs. normal extracellular matrix (ECM), as well as a new animal model of chronic obstructive bladder disease (COBD) which retains its pathologic features even after bladder de-obstruction. Cell models from human and murine hypospadias or genital tubercles (GT) were used to illustrate developmental responses and epigenetic dependency of key developmental genes. Finally, using bladder urothelial and organoid culture systems, we examined activity of epigenetic machinery in response to non uropathogenic vs. uropathogenic E.coli (UPEC). DNMT and EZH2 expression and function were interrogated in these model systems.

RESULTS

Disordered ECM exerted a principal mitogenic and epigenetic role for on bladder smooth muscle both in vitro and in CODB in vivo. Key genes, e.g., BDNF and KCNB2 were under epigenetic regulation in actively evolving obstruction and COBD, though each condition showed distinct epigenetic responses. In models of hypospadias, estrogen strongly dysregulated WNT and Hox expression, which was normalized by epigenetic inhibition. Finally, DNA methylation machinery in the urothelium showed specific activation when challenged by uropathogenic E.coli. Similarly, UPEC induces hypermethylation and downregulation of the growth suppressor p16INK4A. Moreover, host cells exposed to UPEC produced secreted factors inducing epigenetic responses transmissible from one affected cell to another without ongoing bacterial presence.

DISCUSSION

Microenvironmental influences altered epigenetic activity in the three described urologic contexts. Considering that many obstructed bladders continue to display abnormal architecture and dysfunction despite relief of obstruction similar to after resection of posterior valves or BPH, the epigenetic mechanisms described highlight novel approaches for understanding the underlying smooth muscle myopathy of this crucial clinical problem. Similarly, there is evidence for an epigenetic basis of xenoestrogen on development of hypospadias, and UTI-induced pan-urothelial alteration of epigenetic marks and propensity for subsequent (recurrent) UTI. The impact of mechanical, hormonal, infectious triggers on genitourinary epigenetic machinery activity invite novel avenues for targeting epigenetic modifications associated with these non-cancer diseases in urology. This includes the use of deactivated CRISPR-based technologies for precise epigenome targeting and editing. Overall, we underscore the importance of understanding epigenetic regulation in pediatric urology for the development of innovative therapeutic and management strategies.

Altered Urine Microbiome in Male Children and Adolescents with Attention-Deficit Hyperactivity Disorder

While interest in developing the human microbiome as a biomarker for attention-deficit hyperactivity disorder (ADHD) is increasing, there has been limited exploration in utilizing urine samples. In this study, we analysed urine microbiome profiles by extracting 16S ribosomal DNA from purified bacteria-derived extracellular membrane vesicles obtained from urine samples. Sequencing libraries were constructed by amplifying V3-V4 hypervariable regions sequenced using Illumina MiSeq. Profiles of male Korean children and adolescents with ADHD (n = 33) were compared with healthy sex-matched controls (n = 39). Statistically controlling for age, we found decreased alpha diversity in the urine bacteria of the ADHD group, as evidenced by reduced Shannon and Simpson indices (p < 0.05), and significant differences in beta diversity between the two groups (p < 0.001). The phyla Firmicutes and Actinobacteriota, as well as the genera Ralstonia and Afipia, were relatively more abundant in the ADHD group. The phylum Proteobacteria and the genera Corynebacterium and Peptoniphilus were more abundant in the control group. Notably, the genus Afipia exhibited significant correlations with the Child Behavior Checklist Attention Problems score and DSM-oriented ADHD subscale. This study is the first to propose the urine microbiome as a potential biomarker for pediatric ADHD.

Profiling the Urobiota in a Pediatric Population with Neurogenic Bladder Secondary to Spinal Dysraphism

The human bladder has been long thought to be sterile until that, only in the last decade, advances in molecular biology have shown that the human urinary tract is populated with microorganisms. The relationship between the urobiota and the development of urinary tract disorders is now of great interest. Patients with spina bifida (SB) can be born with (or develop over time) neurological deficits due to damaged nerves that originate in the lower part of the spinal cord, including the neurogenic bladder. This condition represents a predisposing factor for urinary tract infections so that the most frequently used approach to treat patients with neurogenic bladder is based on clean intermittent catheterization (CIC). In this study, we analyzed the urobiota composition in a pediatric cohort of patients with SB compared to healthy controls, as well as the urobiota characteristics based on whether patients received CIC or not.

Urinary microbiota of women with recurrent urinary tract infection: collection and culture methods

INTRODUCTION AND HYPOTHESIS

Many clinicians utilize standard culture of voided urine to guide treatment for women with recurrent urinary tract infections (RUTI). However, despite antibiotic treatment, symptoms may persist and events frequently recur. The cyclic nature and ineffective treatment of RUTI suggest that underlying uropathogens pass undetected because of the preferential growth of Escherichia coli. Expanded quantitative urine culture (EQUC) detects more clinically relevant microbes. The objective of this study was to assess how urine collection and culture methods influence microbial detection in RUTI patients.

METHODS

This cross-sectional study enrolled symptomatic adult women with an established RUTI diagnosis. Participants contributed both midstream voided and catheterized urine specimens for culture via both standard urine culture (SUC) and EQUC. Presence and abundance of microbiota were compared between culture and collection methods.

RESULTS

Forty-three symptomatic women participants (mean age 67 years) contributed specimens. Compared to SUC, EQUC detected more unique bacterial species and consistently detected more uropathogens from catheterized and voided urine specimens. For both collection methods, the most commonly detected uropathogens by EQUC were E. coli (catheterized: n = 8, voided: n = 12) and E. faecalis (catheterized: n = 7, voided: n = 17). Compared to catheterized urine samples assessed by EQUC, SUC often missed uropathogens, and culture of voided urines by either method yielded high false-positive rates.

CONCLUSIONS

In women with symptomatic RUTI, SUC and assessment of voided urines have clinically relevant limitations in uropathogen detection. These results suggest that, in this population, catheterized specimens analyzed via EQUC provide clinically relevant information for appropriate diagnosis.

Emerging Role of Microbiome in the Prevention of Urinary Tract Infections in Children

The microbiome of the urinary tract plays a significant role in maintaining health through the impact on bladder homeostasis. Urobiome is of great importance in maintaining the urothelial integrity and preventing urinary tract infection (UTI), as well as promoting local immune function. Dysbiosis in this area has been linked to an increased risk of UTIs, nephrolithiasis, and dysfunction of the lower urinary tract. However, the number of studies in the pediatric population is limited, thus the characteristic of the urobiome in children, its role in a child's health, and pediatric urologic diseases are not completely understood. This review aims to characterize the healthy urobiome in children, the role of dysbiosis in urinary tract infection, and to summarize the strategies to modification and reshape disease-prone microbiomes in pediatric patients with recurrent urinary tract infections.

The microbiome and host mucosal interactions in urinary tract diseases

The urinary tract consists of the bladder, ureters, and kidneys, and is an essential organ system for filtration and excretion of waste products and maintaining systemic homeostasis. In this capacity, the urinary tract is impacted by its interactions with other mucosal sites, including the genitourinary and gastrointestinal systems. Each of these sites harbors diverse ecosystems of microbes termed the microbiota, that regulates complex interactions with the local and systemic immune system. It remains unclear whether changes in the microbiota and associated metabolites may be a consequence or a driver of urinary tract diseases. Here, we review the current literature, investigating the impact of the microbiota on the urinary tract in homeostasis and disease including urinary stones, acute kidney injury, chronic kidney disease, and urinary tract infection. We propose new avenues for exploration of the urinary microbiome using emerging technology and discuss the potential of microbiome-based medicine for urinary tract conditions.

Bacterial Colonization as a Possible Source of Overactive Bladder Symptoms in Pediatric Patients: A Literature Review

Overactive Bladder (OAB) is a common condition that is known to have a significant impact on daily activities and quality of life. The pathophysiology of OAB is not completely understood. One of the new hypothetical causative factors of OAB is dysbiosis of an individual urinary microbiome. The major aim of the present review was to identify data supporting the role of bacterial colonization in overactive bladder symptoms in children and adolescents. The second aim of our study was to identify the major gaps in current knowledge and possible areas for future clinical research. There is a growing body of evidence indicating some relationship between qualitative and quantitative characteristics of individual urinary microbiome and OAB symptoms in adult patients. There are no papers directly addressing this issue in children or adolescents. After a detailed analysis of papers relating urinary microbiome to OAB, the authors propose a set of future preclinical and clinical studies which could help to validate the concept in the pediatric population.

Perspectives from the Society for Pediatric Research: Probiotic use in urinary tract infections, atopic dermatitis, and antibiotic-associated diarrhea: an overview

Probiotics have received significant attention within both the scientific and lay communities for their potential health-promoting properties, including the treatment or prevention of various conditions in children. In this article, we review the published data on use of specific probiotic strains for three common pediatric conditions: the prevention of urinary tract infections and antibiotic-associated diarrhea and the treatment of atopic dermatitis. Research into the utility of specific probiotic strains is of varying quality, and data are often derived from small studies and case series. We discuss the scientific merit of these studies, their overall findings regarding the utility of probiotics for these indications, issues in reporting of methods, and results from these clinical trials, as well as future areas of investigation.

Oligosaccharides and Complex Carbohydrates: A New Paradigm for Cranberry Bioactivity

Cranberry is a well-known functional food, but the compounds directly responsible for many of its reported health benefits remain unidentified. Complex carbohydrates, specifically xyloglucan and pectic oligosaccharides, are the newest recognized class of biologically active compounds identified in cranberry materials. Cranberry oligosaccharides have shown similar biological properties as other dietary oligosaccharides, including effects on bacterial adhesion, biofilm formation, and microbial growth. Immunomodulatory and anti-inflammatory activity has also been observed. Oligosaccharides may therefore be significant contributors to many of the health benefits associated with cranberry products. Soluble oligosaccharides are present at relatively high concentrations (~20% w/w or greater) in many cranberry materials, and yet their possible contributions to biological activity have remained unrecognized. This is partly due to the inherent difficulty of detecting these compounds without intentionally seeking them. Inconsistencies in product descriptions and terminology have led to additional confusion regarding cranberry product composition and the possible presence of oligosaccharides. This review will present our current understanding of cranberry oligosaccharides and will discuss their occurrence, structures, ADME, biological properties, and possible prebiotic effects for both gut and urinary tract microbiota. Our hope is that future investigators will consider these compounds as possible significant contributors to the observed biological effects of cranberry.

A Prospective Study of the Urinary and Gastrointestinal Microbiome in Prepubertal Males

OBJECTIVE

To determine if urinary microbial communities similar to those described in adults exist in children and to profile the urinary and gastrointestinal microbiome in children presenting to urology for both routine and complex urologic procedures.

METHODS

Prepubertal boys (n = 20, ages 3 months-8 years; median age 15 months) who required elective urologic procedures were eligible. Urine samples were collected via sterile catheterization and fecal samples were obtained by rectal swabs. DNA was extracted from urine pellet and fecal samples and subjected to bacterial profiling via 16S rDNA Illumina sequencing and 16S rDNA quantitative polymerase chain reaction. We assessed within and between sample diversity and differential species abundance between samples.

RESULTS

Urine samples had low bacterial biomass that reflected the presence of bacterial populations. The most abundant genera detected in urine samples are not common to skin microbiota and several of the genera have been previously identified in the urinary microbiome of adults. We report presumably atypical compositional differences in both the urinary and gastrointestinal microbiome in children with prior antibiotic exposure and highlight an important case of a child who had undergone lifelong antibiotic treatment as prophylaxis for congenital abnormalities.

CONCLUSION

This study provides one of the first characterizations of the urinary microbiome in prepubertal males. Defining the baseline healthy microbiome in children may lay the foundation for understanding the long-term impact of factors such as antibiotic use in the development of a healthy microbiome as well as the development of future urologic and gastrointestinal diseases.

The local microbiome after pediatric bladder augmentation: intestinal segments and the native urinary bladder host similar mucosal microbiota

INTRODUCTION

Next-generation sequencing (NGS) techniques have provided novel insights into the microbiome of the urinary bladder (UB). In children after bladder augmentation using either ileum (ileocystoplasty, ICP) or colon (colocystoplasty, CCP), the fate of the mucosal microbiome introduced into the urinary tract remains unknown.

OBJECTIVE

The aim was to compare the mucosal microbiome of the native UB vs the augmented intestinal segment (IS) using NGS.

STUDY DESIGN

Twelve children after bladder augmentation (ICP n = 6, CCP n = 6) were included. Biopsies were taken during routine postoperative cystoscopy from the native UB and the IS. Specimens underwent whole-genome DNA extraction, 16S rRNA gene amplification, NGS, and Quantitative Insights Into Microbial Ecology (QIIME) data analysis. Downstream statistical data analyses were performed in Calypso.

RESULTS

Patients' median age at the time of surgery was 11 years (6-17 years), and the median interval between augmentation and sampling was 7 years (4-13 years). α-Diversity (Shannon diversity index) was not significantly different between IS vs UB, ICP vs CCP, and male vs female. No general differences in the overall bacterial pattern (β-diversity) were found between IS, UB, ICP, and CCP groups. The groups overlapped in principal coordinate analysis (PCoA) and non-metric multidimensional scaling (NMDS) analysis (Figure). Age at sampling had a statistically significant influence on β-diversity at the genus level. Corynebacterium, Pseudoxanthomonas, Lactobacillus, Flavobacterium, and Micrococcus were the most dominating taxa detected over all samples. There was an obvious dominance of the genus Corynebacterium in the samples taken from the UB and IS in both ICP and CCP patients. Limitations of this study include the relatively small number of patients.

CONCLUSION

After bladder augmentation, the native UB and augmented ISs (ICP and CCP) host similar microbiota despite their distinct differences of originating mucosal anatomy.