Bacterial vaginosis
Encyclopedia
Bacterial vaginosis or less commonly vaginal bacteriosis is a disease
of the vagina
caused by bacteria
. The U.S. Centers for Disease Control and Prevention
(CDC) states it is not clear what role sexual activity plays in the development. However, it is known that BV is associated with having a new sex partner or having multiple sex partners. BV is caused by an imbalance of naturally occurring bacterial flora and is often confused with yeast infection (candidiasis
), or infection with Trichomonas vaginalis
(trichomoniasis
), which are not caused by bacteria.
. By contrast, the normal vaginal discharge will vary in consistency and amount throughout the menstrual cycle
and is at its clearest about 2 weeks before the period
starts.
, Bacteroides
, and Mycoplasma
. A change in normal bacterial flora including the reduction of lactobacillus, which may be due to the use of antibiotics or pH imbalance, allows more resistant bacteria to gain a foothold and multiply.
Although BV can be associated with sexual activity, there is no clear evidence of sexual transmission. It is possible for sexually inactive persons to get infected with bacterial vaginosis. Rather, BV is a disordering of the chemical and biological balance of the normal flora. Recent research is exploring the link between sexual partner treatment and eradication of recurrent cases of BV. Pregnant
women and women with sexually transmitted infections are especially at risk for getting this infection. Bacterial vaginosis may sometimes affect women after menopause
. A 2005 study by researchers at Ghent University
in Belgium showed that subclinical iron deficiency (anemia
) was a strong predictor of bacterial vaginosis in pregnant women. A longitudinal study published in February 2006 in the American Journal of Obstetrics and Gynecology showed a link between psychosocial stress and bacterial vaginosis independent of other risk factors.
Two positive results in addition to the discharge itself are enough to diagnose BV. If there is no discharge, then all three criteria are needed.
Differential diagnosis for bacterial vaginosis includes the following:
At least three of the four criteria should be present for a confirmed diagnosis.
What this technique loses in interobserver reliability, it makes up in ease and speed of use.
The standards for research are the Nugent Criteria. In this scale, a score of 0-10 is generated from combining three other scores. This method is time consuming and requires trained staff, but it has high interobserver reliability. The scores are as follows:
At least 10–20 high power (1000× oil immersion) fields are counted and an average determined.
A recent study compared the Gram stain using the Nugent criteria and the DNA hybridization test Affirm VPIII in diagnosing BV. The Affirm VPIII test detected Gardnerella in 107 (93.0%) of 115 vaginal specimens positive for BV diagnosed by Gram stain. The Affirm VPIII test has a sensitivity of 87.7% and specificity of 96% and may be used for the rapid diagnosis of BV in symptomatic women.
or clindamycin
either orally or vaginally are effective treatment. However, there is a high rate of recurrence.
The usual medical regimen for treatment is the antibiotic Metronidazole (500 mg twice a day, once every 12 hours) for 7 days. A one-time 2g dose is no longer recommended by the CDC because of low efficacy. Extended release metronidazole is an alternative recommendation.
In contrast to some other infectious diseases affecting the female genitals, according to some sources, treatment of the sexual partners is not necessarily recommended.
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
of the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
caused by bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. The U.S. Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
(CDC) states it is not clear what role sexual activity plays in the development. However, it is known that BV is associated with having a new sex partner or having multiple sex partners. BV is caused by an imbalance of naturally occurring bacterial flora and is often confused with yeast infection (candidiasis
Candidiasis
Thrush redirects here. For the hoof infection see Thrush .Candidiasis or thrush is a fungal infection of any of the Candida species , of which Candida albicans is the most common...
), or infection with Trichomonas vaginalis
Trichomonas vaginalis
Trichomonas vaginalis is an anaerobic, flagellated protozoan, a form of microorganism. The parasitic microorganism is the causative agent of trichomoniasis, and is the most common pathogenic protozoan infection of humans in industrialized countries. Infection rates between men and women are the...
(trichomoniasis
Trichomoniasis
Trichomoniasis, sometimes referred to as "trich", is a common cause of vaginitis. It is a sexually transmitted disease, and is caused by the single-celled protozoan parasite Trichomonas vaginalis producing mechanical stress on host cells and then ingesting cell fragments after cell death...
), which are not caused by bacteria.
Symptoms and signs
The most common symptom of BV is an abnormal homogeneous off-white vaginal discharge (especially after sex) with an unpleasant smell. This malodorous discharge coats the walls of the vagina, and is usually without irritation, pain or erythemaErythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
. By contrast, the normal vaginal discharge will vary in consistency and amount throughout the menstrual cycle
Menstrual cycle
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
and is at its clearest about 2 weeks before the period
Menstruation
Menstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...
starts.
Causes
A healthy vagina normally contains many microorganisms; some of the common ones are Lactobacillus crispatus and Lactobacillus jensenii. Lactobacilli, particularly hydrogen peroxide-producing species, appear to help prevent other vaginal microorganisms from multiplying to a level where they cause symptoms. The microorganisms involved in BV are very diverse, but include Gardnerella vaginalis, MobiluncusMobiluncus
Mobiluncus is a genus of gram-positive, anaerobic, rod-shaped bacteria. While this species of bacterium possesses a cell wall with structural similarity to other gram-positive cell walls, upon gram stain these bacteria may be stained either gram-negative or gram-variable.Its organisms are found in...
, Bacteroides
Bacteroides
Bacteroides is a genus of Gram-negative, bacillus bacteria. Bacteroides species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids...
, and Mycoplasma
Mycoplasma
Mycoplasma refers to a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogenic in humans,...
. A change in normal bacterial flora including the reduction of lactobacillus, which may be due to the use of antibiotics or pH imbalance, allows more resistant bacteria to gain a foothold and multiply.
Although BV can be associated with sexual activity, there is no clear evidence of sexual transmission. It is possible for sexually inactive persons to get infected with bacterial vaginosis. Rather, BV is a disordering of the chemical and biological balance of the normal flora. Recent research is exploring the link between sexual partner treatment and eradication of recurrent cases of BV. Pregnant
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
women and women with sexually transmitted infections are especially at risk for getting this infection. Bacterial vaginosis may sometimes affect women after menopause
Menopause
Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...
. A 2005 study by researchers at Ghent University
Ghent University
Ghent University is a Dutch-speaking public university located in Ghent, Belgium. It is one of the larger Flemish universities, consisting of 32,000 students and 7,100 staff members. The current rector is Paul Van Cauwenberge.It was established in 1817 by King William I of the Netherlands...
in Belgium showed that subclinical iron deficiency (anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
) was a strong predictor of bacterial vaginosis in pregnant women. A longitudinal study published in February 2006 in the American Journal of Obstetrics and Gynecology showed a link between psychosocial stress and bacterial vaginosis independent of other risk factors.
Diagnosis
To make a diagnosis of bacterial vaginosis, a swab from inside the vagina should be obtained. These swabs should be tested for:- A characteristic "fishy" odor on wet mount. This test, called the whiff test, is performed by adding a small amount of potassium hydroxidePotassium hydroxidePotassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
to a microscopic slide containing the vaginal discharge. A characteristic fishy odor is considered a positive whiff test and is suggestive of bacterial vaginosis. - Loss of acidity. To control bacterial growth, the vagina is normally slightly acidic with a pHPHIn chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of 3.8–4.2. A swab of the discharge is put onto litmus paper to check its acidity. A pH greater than 4.5 is considered alkaline and is suggestive of bacterial vaginosis. - The presence of clue cellClue cellClue cells are epithelial cells of the vagina that get their distinctive stippled appearance by being covered with bacteria.They are a medical sign of bacterial vaginosis, particularly that caused by Gardnerella vaginalis, a group of Gram-variable bacteria...
s on wet mount. Similar to the whiff test, the test for clue cells is performed by placing a drop of sodium chlorideSodium chlorideSodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
solution on a slide containing vaginal discharge. If present, clue cells can be visualized under a microscope. They are so-named because they give a clue to the reason behind the discharge. These are epithelial cells that are coated with bacteria.
Two positive results in addition to the discharge itself are enough to diagnose BV. If there is no discharge, then all three criteria are needed.
Differential diagnosis for bacterial vaginosis includes the following:
- Normal discharge.
- CandidiasisCandidiasisThrush redirects here. For the hoof infection see Thrush .Candidiasis or thrush is a fungal infection of any of the Candida species , of which Candida albicans is the most common...
(thrush, or a yeast infection). - TrichomoniasisTrichomoniasisTrichomoniasis, sometimes referred to as "trich", is a common cause of vaginitis. It is a sexually transmitted disease, and is caused by the single-celled protozoan parasite Trichomonas vaginalis producing mechanical stress on host cells and then ingesting cell fragments after cell death...
, an infection caused by Trichomonas vaginalisTrichomonas vaginalisTrichomonas vaginalis is an anaerobic, flagellated protozoan, a form of microorganism. The parasitic microorganism is the causative agent of trichomoniasis, and is the most common pathogenic protozoan infection of humans in industrialized countries. Infection rates between men and women are the...
.
In clinical practice
In clinical practice BV is diagnosed using the Amsel criteria:- Thin, white, yellow, homogeneous discharge
- Clue cellClue cellClue cells are epithelial cells of the vagina that get their distinctive stippled appearance by being covered with bacteria.They are a medical sign of bacterial vaginosis, particularly that caused by Gardnerella vaginalis, a group of Gram-variable bacteria...
s on microscopyMicroscopyMicroscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye... - pHPHIn chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of vaginal fluid >4.5 - Release of a fishy odor on adding alkaliAlkaliIn chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...
—10% potassium hydroxidePotassium hydroxidePotassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
(KOH) solution.
At least three of the four criteria should be present for a confirmed diagnosis.
Gram stain
An alternative is to use a Gram-stained vaginal smear, with the Hay/Ison criteria or the Nugent criteria. The Hay/Ison criteria are defined as follows:- Grade 1 (Normal): LactobacillusLactobacillusLactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...
morphotypes predominate. - Grade 2 (Intermediate): Mixed flora with some Lactobacilli present, but Gardnerella or Mobiluncus morphotypes also present.
- Grade 3 (Bacterial Vaginosis): Predominantly Gardnerella and/or Mobiluncus morphotypes. Few or absent Lactobacilli. (Hay et al., 1994)
What this technique loses in interobserver reliability, it makes up in ease and speed of use.
The standards for research are the Nugent Criteria. In this scale, a score of 0-10 is generated from combining three other scores. This method is time consuming and requires trained staff, but it has high interobserver reliability. The scores are as follows:
- 0–3 is considered negative for BV
- 4–6 is considered intermediate
- 7+ is considered indicative of BV.
At least 10–20 high power (1000× oil immersion) fields are counted and an average determined.
Lactobacillus morphotypes — average per high powered (1000× oil immersion) field. View multiple fields. |
Gardnerella Gardnerella Gardnerella is a genus of gram-variable-staining facultative anaerobic bacteria of which G. vaginalis is the only species.Once classified as Haemophilus vaginalis and afterwards as Corynebacterium vaginalis, Gardnerella vaginalis grows as small, circular, convex, gray colonies on chocolate agar; it... / Bacteroides Bacteroides Bacteroides is a genus of Gram-negative, bacillus bacteria. Bacteroides species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids... morphotypes — average per high powered (1000× oil immersion) field. View multiple fields. |
Curved Gram variable rods — average per high powered (1000× oil immersion) field. View multiple fields (note that this factor is less important — scores of only 0–2 are possible) |
|
|
A recent study compared the Gram stain using the Nugent criteria and the DNA hybridization test Affirm VPIII in diagnosing BV. The Affirm VPIII test detected Gardnerella in 107 (93.0%) of 115 vaginal specimens positive for BV diagnosed by Gram stain. The Affirm VPIII test has a sensitivity of 87.7% and specificity of 96% and may be used for the rapid diagnosis of BV in symptomatic women.
Antibiotics
MetronidazoleMetronidazole
Metronidazole is a nitroimidazole antibiotic medication used particularly for anaerobic bacteria and protozoa. Metronidazole is an antibiotic, amebicide, and antiprotozoal....
or clindamycin
Clindamycin
Clindamycin rINN is a lincosamide antibiotic. It is usually used to treat infections with anaerobic bacteria but can also be used to treat some protozoal diseases, such as malaria...
either orally or vaginally are effective treatment. However, there is a high rate of recurrence.
The usual medical regimen for treatment is the antibiotic Metronidazole (500 mg twice a day, once every 12 hours) for 7 days. A one-time 2g dose is no longer recommended by the CDC because of low efficacy. Extended release metronidazole is an alternative recommendation.
In contrast to some other infectious diseases affecting the female genitals, according to some sources, treatment of the sexual partners is not necessarily recommended.