Laboratory diagnosis of Bacterial vaginosis caused by Gardnerella vaginalis


Bacterial vaginosis (BV) is a common condition that affects many women of reproductive age. It is caused by an imbalance of the normal vaginal flora, which leads to an overgrowth of certain bacteria, especially Gardnerella vaginalis. G. vaginalis is a gram-variable rod-shaped bacterium that can adhere to the epithelial cells of the vagina and form a biofilm. This biofilm disrupts the protective function of the vaginal mucosa and increases the risk of infection and inflammation.

BV is associated with various symptoms and complications, such as:

  • A thin, white or gray vaginal discharge with a fishy odor
  • Vaginal itching, burning or irritation
  • Pain during urination or sexual intercourse
  • Increased susceptibility to sexually transmitted infections (STIs), such as chlamydia, gonorrhea, herpes and HIV
  • Increased risk of pelvic inflammatory disease (PID), which can cause infertility, ectopic pregnancy and chronic pelvic pain
  • Increased risk of adverse pregnancy outcomes, such as preterm birth, low birth weight and intrauterine infection

The exact cause of BV is not fully understood, but it is thought to be influenced by various factors, such as:

  • Sexual activity: Having multiple or new sexual partners, or having sex with a partner who has BV, can increase the chance of getting BV. However, BV can also occur in women who are not sexually active.
  • Hormonal changes: Fluctuations in estrogen and progesterone levels during the menstrual cycle, pregnancy or menopause can affect the vaginal pH and flora.
  • Hygiene practices: Douching, using scented soaps or feminine products, or wearing tight or synthetic underwear can alter the vaginal environment and favor the growth of G. vaginalis and other bacteria.
  • Antibiotic use: Taking antibiotics for other infections can kill the beneficial lactobacilli that normally keep the vaginal flora in balance and prevent BV.

The diagnosis of BV is based on a combination of clinical and laboratory criteria. The most commonly used methods are:

  • The Amsel criteria: These are four clinical signs that indicate BV: a) a thin, white or gray discharge; b) a vaginal pH above 4.5; c) a positive whiff test (a fishy odor when adding potassium hydroxide to the discharge); and d) the presence of clue cells (epithelial cells covered with bacteria) on microscopic examination of the discharge.
  • The Nugent score: This is a quantitative method that involves grading a gram stain of the vaginal smear according to the number and type of bacteria present. A score of 0 to 3 indicates normal flora; a score of 4 to 6 indicates intermediate flora; and a score of 7 to 10 indicates BV.

The treatment of BV aims to restore the normal vaginal flora and prevent complications. The most effective antibiotics for BV are metronidazole and clindamycin, which can be taken orally or applied topically. However, recurrence rates are high, and some women may need repeated or prolonged courses of therapy. Alternative treatments, such as probiotics, boric acid or hydrogen peroxide, have been suggested but their efficacy and safety are not well established.

BV is a common and treatable condition that can have serious consequences if left untreated. Therefore, it is important for women to be aware of the signs and symptoms of BV and seek medical attention if they suspect they have it. Moreover, preventive measures, such as practicing safe sex, avoiding douching and using unscented products, can help maintain a healthy vaginal flora and reduce the risk of BV.