An Overview of the Microbiota of the Human Urinary Tract in Health and Disease: Current Issues and Perspectives

Abstract

This article is intended to deepen our knowledge to date regarding the functions of the resident microbiota/microbiome in the urinary system for human health and disease. First, we sought to report the general characteristics (composition and stability) of the normal urinary system microbiota in the different anatomical sites in relation to some factors such as the effect of age, gender and diet, analyzing in detail the functions and the composition of the microbiota in the light of current knowledge. Several pieces of evidence suggest the importance of preserving the micro-ecosystem of the urinary system, and in some cases their relationship with diseases is important for maintaining human health is well understood. The female and male reproductive microbiota have mainly been studied over the past decade. In the past, the arrest was thought to have taken place in a sterile environment. Microorganisms of the microbiota form biofilms, three-dimensional structures, that differ in the reproductive organs and interact with both gametes and the embryo as well as with maternal tissues. These biofilms from the reproductive system also interact with others, such as that of the gastrointestinal tract. Reduction in its diversity intestinal microbiota can disrupt estrogen metabolism and affect the reproductive microbiota. It is therefore understood that its quantitative and qualitative identification is important for microbiota, but also the study of the structures formed by the microorganisms. A dysbiosis with local or systemic causes can lead to serious diseases. The role of probiotics in maintaining microbial population harmony (eubiosis) and preventing certain pathologies of the urinary and reproductive system was also investigated. A negative variation in the qualitative and quantitative composition of certain strains of microorganisms (dysbiosis) due to local or systemic causes can even lead to serious diseases. The role of probiotics in maintaining the healthy balance of microorganism populations (eubiosis), and thus in the prevention of certain pathologies of the urinary and reproductive system, has also been studied.

Keywords: bladder cancer; dysbiosis; estrogen metabolism; human microbiota; immune modulation; probiotics; urgency incontinence; urinary system diseases; urinary system microbiota; urinary tract infections.

Figure 1

There are differences in composition between the microbiota and age. The figure indicates the microbial composition between two age groups (20–49 and age ≥70) on a certain sample of women without urinary pathologies. The orange circle indicates the common bacteria found in all ages groups while the green circle indicates the common bacteria, between the two age groups (20–49 and age ≥70). The yellow circle indicates bacteria present in the age range 20–49 and the blue circle the age range ≥70 [16].

Figure 2

One possible mechanism or the carcinogenesis from F. nucleatum. FadA, F. nucleatum adhesin, binds to β-catenin on the surface of tumor cells and activates oncogenic Wnt/β-catenin signaling. F. nucleatum can also affect the function of lymphocytes and natural killer cells by binding to the TIGIT receptor (expressed on all NK cells, as well as on other immune cells) and through another adhesion FAP2 also binds to a disaccharide (Gal-GalNAc), which is expressed on the surface of several neoplastic and other cells, facilitating the binding of F. nucleatum to colon cancer cells.

Figure 3

Microbial species detected among definitive studies in the microbiota of the nomal human vagina.

Figure 4

Main commercial probiotic species used.