The microbiota is the set of microorganisms that inhabit all healthy tissues of our body. Since it was described by Albert Döderlein in 1891, the existence of a "vaginal flora" or "Döderlein's flora" has been known, which is mainly composed of bacteria of the genus LactobacillusWe now know that all our tissues and fluids are inhabited by micro-organisms, even those that were considered "sterile" until recently, such as the placenta, amniotic fluid, amniotic fluid, amniotic fluid, placenta, amniotic fluid and bacteria. Today, we know that all our tissues and fluids are inhabited by micro-organisms, even those that were considered "sterile" until recently, such as the placenta, amniotic fluid, urine or the nervous system.
What is the genito-urinary microbiota?
Until recently, it was thought that urine was sterile and that bacteria and other germs did not exist in the urinary tract. Today, thanks to molecular biology and genomic amplification techniques that allow us to detect microorganisms that do not grow in conventional culture media, we know that there is a very varied microbiota at the urinary level, and that it is not the same as the genital microbiota. However, although the urinary and female genital systems do not share the same microbiota, the composition of one may be influenced by the composition of the other.
In the case of the vaginal microbiota, six "vaginotypes" have been described, depending on the predominance of certain microorganisms (see table n°1). I will not go into a detailed description of these vaginotypes, but it is important to note that, depending on the predominant type of germ, there will be a greater or lesser production of lactic acid, which will regulate the vaginal pH and, therefore, the micro-organisms that will reside there. The higher the acidity, the lower the risk of vaginal colonisation by uropathogenic germs, which do not tolerate very low pH. This is why women with vaginotype I, where the Lactobacillus crispatusvaginotype IVb, which has the highest lactic acid production and therefore the most acidic pH (about 4), is the group of women with the lowest prevalence of urine infections and viral sexually transmitted diseases. On the opposite side we find vaginotype IVb, composed mainly of non-lactobacillary bacteria, and with a pH around 5.3. This higher pH predisposes to urine infections, sexually transmitted diseases and vaginal infections (vaginosis).
It should also be noted that the composition of the vaginal microbiota changes over the course of a woman's life, depending on her hormonal status. The thickness of the vaginal mucosa, its glycogen (sugar) content and menstrual cycles influence the type of germs that predominate at any given time, as lactobacilli feed on the cells that are shed from the vaginal wall and the glycogen they contain. This is why the incidence of cystitis increases with age, especially after the menopause, as the absence of oestrogen (female hormones) stimulus thins the vaginal wall and means that the cells are less glycogen-loaded. With less nourishment, the concentration of lactobacilli decreases and, consequently, the production of lactic acid. This is why the application of hormonal gels in the vagina, which improve the condition of the vaginal wall, has proven to be an effective measure against urinary tract infections in post-menopausal women. This also helps to understand why some young patients often suffer from infections in the days before menstruation or ovulation: at these times, there is a sharp drop in oestrogen levels in the blood, and thus a thinning of the vaginal wall, with a consequent decrease in vaginal lactobacilli. Thus, there is less protection against uropathogenic germs during these days.
In addition to hormonal changes and changes in the vaginal microbiota, there are other factors that can alter the vaginal pH and promote urine infections in women: sexual intercourse and excessive intravaginal hygiene, as well as vaginal douching. It is very common to find patients who suffer from UTIs almost systematically after sexual intercourse. The short length of the female urethra and the "rubbing" that occurs during intercourse have always been blamed. What many people do not know, however, is that semen is much more alkaline than the vagina, with a pH between 7.2 and 8 generally, sometimes even higher. Because of this, intravaginal ejaculation can quickly raise the pH and thus encourage the development of uropathogenic bacteria. Similarly, although it may seem paradoxical, excessive use of alkaline pH soaps (which are the majority) or vaginal douching in the genital area can also alter vaginal acidity and cause an imbalance in the vaginal microbiota.
As for the urinary microbiota, we are gradually gaining more extensive knowledge about it. It is known, for example, that it changes with age in both sexes, as it does in the vagina. Recently, seven "urotypes" of female microbiota have been described, which are named according to the dominant gender or family (see table 2).
In humans, the genitourinary microbiota has been much less studied. Some common micro-organisms are known, such as Lactobacillus, Sneathia, Veillonella, Corynebacterium, Prevotella,
Streptococcus y Ureaplasma. These micro-organisms are found in both urine and urethra. Six urotypes have recently been described in humans (see table 3).
In the case of the prostate, we find a somewhat different microbiota with genera such as Oceanobacillus, Paenibacillus, Streptococcus, Carnobacterium, Alkaliphilus, Cronobacter, Lactococcus, Enterococcus o Bacillus. We still have little knowledge about the role of the different micro-organisms that make up the urinary microbiota. What is important to note, in both men and women, is that many of the germs that we consider "pathogenic" such as Escherichia o Streptococcus can naturally belong to a person's microbiota without causing disease. Hence the importance, and I will never tire of saying it, of not treating asymptomatic bacteriuria.
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