Vaginal microbiota and probiotics

The vaginal microbiota is the set of microorganisms that live in the vagina of women and that have a beneficial effect. Formerly it was called vaginal flora. The first microbiological study of the vagina was published by Döderlein in 1892 describing lactobacilli and therefore they are also called Döderlein bacilli. They are elongated bacteria, therefore they are bacilli, and they produce lactic acid, hence the name lactobacilli.

  • The lactobacilli present in the woman’s vagina and that make up the vaginal microbiota (flora) are beneficial by preventing infections by microorganisms capable of producing them.
  • The study of the vaginal microbiota has given way to treatment with probiotics, live microorganisms that, when administered in adequate amounts, exert a beneficial effect on health.
  • In gynecology, probiotics have been shown to be effective as adjuvants in the treatment of the most frequent vaginal infections.

Beneficial bacteria for the vaginal microbiota

Several different types of lactobacilli have been described in the vagina of women. These bacteria are beneficial for vaginal health and in most cases do not have the ability to cause infections since in order to reproduce quickly they have lost much of their DNA and, among the properties they have lost, is to invade the human body . Only in some cases of patients with diseases that produce a very important immunosuppression or terminal patients has a case of significant infection by lactobacilli been described.
Lactobacilli are bacteria present mainly in the vagina of women of childbearing age. During childhood and after menopause the presence of lactobacilli in the vagina is much lower. They are considered beneficial microorganisms for health because they prevent infections by microorganisms with the potential to produce infections. They do this in two different ways:

  • The cells of the vaginal walls have receptors to which bacteria bind like a key to a lock. Lactobacilli have on their surface proteins called adhesins that bind to these receptors in the mucosa of the vagina so that the microorganisms that cause infections cannot bind to them and thus cannot cause disease, it is a competition for the receptors. The vaginal microbiota forms a film on the mucosa of the vagina that prevents the attachment of harmful bacteria.
  • Lactobacilli feed on the glucose reserves in the cells of the walls of the vagina, glycogen. They have a fermentative metabolism and, from glycogen, produce lactic acid, in such a way that the vaginal pH decreases, remaining at a pH between 3.5 and 4. This acidic environment destroys many of the bacteria that colonize the vagina from the digestive tract and prevents vaginal infections from them. Also, many urinary infections are caused by bacteria from the digestive tract that pass into the vagina and from there to the urethra and bladder from urine. The presence of lactobacilli destroys part of these bacteria that come from the rectum and reduces urine infections. Some lactobacilli also produce hydrogen peroxide which is an antiseptic because it damages the DNA of harmful bacteria.

Lactobacilli in the life of women

Lactobacilli are more frequent in women of childbearing age since the estrogens secreted by the ovaries have an effect on the vaginal mucosa. Under the effect of these hormones the mucosa of the vagina of the fertile woman undergoes a thickening and an increase of the glucose reserves in the form of glycogen. Under these conditions, lactobacilli develop better and colonize the vagina. During menopause, the mucosa thins and the level of glycogen decreases, which is why lactobacilli decrease and bacterial infections from the digestive tract and urinary tract infections are more frequent. For this reason, in women who have vaginal atrophy and have no contraindication for it, it is recommended to do a local treatment with estrogens.


The study of the vaginal microbiota has given way to treatment with probiotics . These are defined as living microorganisms that, when administered in adequate quantities, exert a beneficial effect on health. They must be differentiated from prebiotics, which are indigestible compounds that stimulate the production of indigenous microbiota. In other words, probiotics are directly bacteria and prebiotics are the food for these bacteria.
The first attempt to use probiotics that we have evidence of is with Newman in 1915 when he injected them into the bladder of urine to treat cystitis. Until a few years ago, good results were not achieved with probiotic treatments because a correct selection of the strains to be administered was not made. The best results have been shown to be achieved with treatments that combine different strains of probiotics.
In mild gynecological infections, probiotics can be a treatment of choice, so that the use of antibiotics is reduced and the dreaded resistance and side effects are avoided. For gynecology, treatments can be done orally in pills, which usually last about 15-30 days, or vaginally in ovules that last between 5 and 15 days.

Its use in gynecology

The use of probiotics in gynecological treatments is on the rise and therefore a consensus has been drawn up on the use of probiotics in gynecology:

  • The autochthonous microbiota helps preserve the vagina from infectious pathologies.
  • Probiotics are effective as adjuvants in the treatment of the most frequent vaginal infections. So that:
  • Improves cure rates for vaginal infections
  • Decrease recurrences of bacterial vaginosis , the most common bacterial infection of the vagina
  • They decrease the recurrences of urinary tract infections.
  • They improve the cure rates of candidal vulvovaginitis.

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