Bacterial vaginosis: Causes, symptoms, and treatments

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Bacterial vaginosis (BV) is the most common cause of vaginitis, affecting 40% to 50% of women of reproductive age.

Bacterial vaginosis causes

When there is an imbalance in the ratio of normal vaginal bacterial flora, BV occurs. Lactobacilli are the most common organisms in the vaginal flora, producing lactic acid that keeps the vaginal pH between 3.8 and 4.5. Furthermore, certain subsets of lactobacilli produce hydrogen peroxide, which prevents the overgrowth of normal vaginal flora. Lactobacilli are replaced by an overgrowth of G. vaginalis, Mobiluncus spp., Prevotella spp., Porphyromonas, Peptostreptococcus, Mycoplasma hominis, and Ureaplasma spp. as the vaginal pH becomes alkaline. This combination of organisms causes malodor and increased abnormal vaginal discharge, which is more noticeable after intercourse.

Risk factors of Bacterial vaginosis

BV is associated with:

  • New or multiple sex partners
  • Frequent douching
  • Use of intrauterine devices
  • Pregnancy
  • Lack of the protective lactobacilli.

There is evidence that BV is a risk factor for premature membrane rupture and preterm labor in pregnant women.

Complications of Bacterial vaginosis

  • Pelvic inflammatory disease
  • Endometritis
  • Increased risk for acquiring some sexually transmitted infections (STIs) such as HIV, N. gonorrhea, C. trachomatis, and HSV-2.

Diagnosis of Bacterial vaginosis

BV is diagnosed by:

  • Examining the vaginal secretions for abnormal appearance or quantity
  • Performing the pH and amine tests
  •  Microscopically observing the wet mount for the presence of clue cells and the absence of WBCs and lactobacilli morphotypes.
Bacterial vaginosis clue cells
Bacterial vaginosis clue cells

Symptoms of Bacterial vaginosis

According to Amsel’s Diagnostic Criteria, three of the following four features must be present for the diagnosis of BV:

  1. Thin, white, homogeneous discharge
  2. Vaginal fluid pH greater than 4.5,
  3. A positive amine (Whiff) test
  4. Presence of clue cells on microscopic examination.

Diagnosis of Bacterial vaginosis

The Gram stain is the gold standard for determining the ratio of each bacterial morphotype and offers a definitive diagnosis. Other tests used to diagnose BV include

  • DNA hybridization probe test
  • Affirm VPIII (Becton, Dickinson), which detects G. vaginalis
  • A proline aminopeptidase test (Pip Activity TestCard, Quidel, San Diego, CA)
  • OSOM BVBLUE test (Genzyme Diagnostics, Cambridge, MA).

How to treat bacterial vaginosis

Women should seek treatment to alleviate vaginal symptoms and lower their risk of infection. Furthermore, the benefits of treatment include lowering the risk of contracting a STI and lowering the risks associated with pregnancy.

The recommended treatments are metronidazole (Flagyl), metronidazole gel, or clindamycin cream.


  1. Egan, MA, and Lipsky, MS: Diagnosis of vaginitis, Am Fam Physician 62(5):1095–1104, Sep 2000. Web site: http://
  2. Clinical and Laboratory Standards Institute. Provider-Performed Microscopy Testing: Approved Guideline, ed. 2. CLSI document POCT10-A2. CLSI, Wayne, PA, 2011.
  3. Metzger, GD: Laboratory diagnosis of vaginal infections. Clin Lab Sci 11:47–52, 1998.
  4. Woods, GL, and Croft, AC: Specimen collection and handling for diagnosis of infectious diseases. In Henry, JB (ed): Clinical Diagnosis and Management by Laboratory Methods, ed 22. Elsevier Saunders, Philadelphia, 2011.
  5. Centers for Disease Control and Prevention: Diseases characterized by vaginal discharge. Sexually Transmitted Diseases Treatment Guidelines, 2010. treatment/2010/vaginal-discharge.htm

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About the Author: Labweeks

KEUMENI DEFFE Arthur luciano is a medical laboratory technologist, community health advocate and currently a master student in tropical medicine and infectious disease.

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