Bacterial Vaginosis - Causes, Symptoms And Treatment

Bacterial vaginosis is a vaginal infection caused by the abnormal proliferation of natural bacteria in the vagina, being the main cause of vaginal discharge in women of childbearing age. Vaginosis is related to the growth of several bacteria, especially one, called Gardnerella vaginalis, which can cause discharge with an unpleasant, fish-like odor.

Bacterial vaginosis
Bacterial vaginosis


The vagina is an organ naturally inhabited by several bacteria, some "good", some "bad". Lactobacilli are the "good" bacteria and are usually found in greater amounts (about 95% of the population), preventing the growth of potentially disease-causing bacteria by controlling vaginal pH and food competition.

Bacterial vaginosis occurs when there is a rupture of this balance, leading to a decrease in lactobacilli and a growth of "bad" flora that may be composed of several bacteria, among them: Gardnerella vaginalis, Prevotella, Porphyromonas, Bacteroides, Peptostreptococcus, Mycoplasma hominis, Ureaplasma urealyticum, Mobiluncus, Fusobacterium and Atopobium vagina. Of all these bacteria, Gardnerella vaginalis appears to be the most characteristic microorganism of vaginosis, being present in more than 96% of the cases.

We do not yet know very well what leads to this deregulation of the natural bacterial flora of the vagina, but some risk factors are already known:
  • Multiple sexual partners
  • Perform vaginal douche frequently
  • Smoking
  • Recent use of antibiotics
  • IUD use

Bacterial vaginosis is a disease typical of women of childbearing age; we do not know why, but it is more common in Afro-descendant women.

The classification of bacterial vaginosis as a sexually transmitted disease (STD) is currently accepted, although it is still controversial. In favor of classification as STD, it is important that promiscuity is one of the risk factors for its development. Another positive fact is the fact that condom use decreases the incidence of this infection. On the other hand, even virgin or unrelated women may develop bacterial vaginosis.


Two out of three women with bacterial vaginosis do not have any type of symptoms. In those with symptoms, the most common is a greyish discharge with strong odor, usually described as fish-smelling discharge. This foul-smelling vaginal discharge usually worsens after intercourse.

Unlike other causes of vaginal discharge that usually occur with vaginitis (inflammation of the vagina), bacterial vaginosis causes little or no inflammation, so it does not usually occur with symptoms of pain, itching or dysuria (pain or discomfort to urinate).


The diagnosis of bacterial vaginosis is based on the set of symptoms and laboratory findings. If you have complaints of discharge, the gynecologist will do a complete gynecological examination and collect samples of the secretions.

By examining secretions it is possible to evaluate the pH of the vagina (which is less acidic in vaginosis) and look for microorganisms through a microscope. In vaginosis there is a simple, in-office test, which consists of adding 10% potassium hydroxide in the vaginal secretion to increase the release of the characteristic strong fish scent.

Through examination under the microscope it is possible to identify the so - called clue-cells , cells typical of bacterial vaginosis. It is also possible to identify other germs that cause discharge other than vaginosis, such as fungi.

The culture of secretions to identify bacteria has no role in diagnosis since up to 60% of women without vaginosis have Gardnerella vaginalis and other bacteria in their vaginas. Having Gardnerella vaginalis does not necessarily mean that the woman will develop vaginosis.


Even in patients without symptoms, vaginosis can cause some complications. These include:
  • Higher risk of contamination by other STDs* in case of contaminated partner
  • Increased risk of STD transmission* to the partner if the patient is infected with an STD
  • Increased risk of pelvic inflammatory disease, especially after gynecological surgeries
  • Higher risk of preterm birth in pregnant women

* DST with increased risk of transmission and contamination:


In about 1/3 of the cases, vaginosis disappears spontaneously, due to the recovery of the lactobacilli population. Therefore, treatment is only indicated if there are symptoms or if the patient is about to undergo gynecological surgery.

The treatment, when indicated, is done with oral or intravaginal antibiotics. The most commonly prescribed are metronidazole or clindamycin for 7 days. Tinidazole or secnidazole are also good options.

When a course of clindamycin is prescribed intravaginally, sexual intercourse with condoms should be avoided for up to five days after the end of treatment, as the antibiotic weakens the latex, reducing its effectiveness as a protective barrier.

Because vaginosis is not necessarily an STD, it is not necessary to treat the partner. There is no evidence that partner treatment influences the cure rate of the patient. In cases of homosexual intercourse between women there is still doubt whether the treatment of the partner is necessary.

The treatment of bacterial vaginosis in asymptomatic pregnant women is controversial, as there is no evidence that it reduces the incidence of preterm deliveries. Currently we only indicate if the pregnant woman is at high risk of preterm birth or have a history of preterm birth related to the presence of vaginosis.

Antibiotic treatment cures vaginosis but does not act directly on its causes. Therefore, the recurrence rate is high, about 30% in three months and up to 50% in one year. Patients with more than three episodes per year benefit from a long-term treatment for up to six months with intravaginal metronidazole.

The consumption of yogurts with lactobacilli is not effective in prevention, since these lactobacilli are different from those that live in the vagina.

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