| Bacterial vaginosis | |
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| Classification and external resources | |
Micrograph of bacterial vaginosis — squamous cells of the cervix covered with rod-shaped bacteria, Gardnerella vaginalis (arrows). |
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| ICD-10 | B96, N76 |
| ICD-9 | 616.1 |
| MeSH | D016585 |
Bacterial vaginosis (BV) or less commonly vaginal bacteriosis[1] is a disease of the vagina caused by bacteria. The 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 classified as an STD by the CDC. [2] [3] 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.[4][5]
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The most common symptom of BV is an abnormal homogeneous off-white vaginal discharge (especially after sex) with an unpleasant smell.[6] This malodorous discharge coats the walls of the vagina, and is usually without irritation, pain or erythema. 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.
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, Mobiluncus, 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.[7] 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.[8] 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.[9]
To make a diagnosis of bacterial vaginosis, a swab from inside the vagina should be obtained. These swabs should be tested for:
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.[10]
Differential diagnosis for bacterial vaginosis includes the following:
In clinical practice BV is diagnosed using the Amsel criteria:[10]
At least three of the four criteria should be present for a confirmed diagnosis.[3]
An alternative is to use a Gram-stained vaginal smear, with the Hay/Ison[11] criteria or the Nugent[12] criteria. The Hay/Ison criteria are defined as follows:[3]
What this technique loses in interobserver reliability, it makes up in ease and speed of use.
The standards for research are the Nugent[12] 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.
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Lactobacillus morphotypes — average per high powered (1000× oil immersion) field. View multiple fields. |
Gardnerella / Bacteroides 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) |
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A recent study [13] 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.
Metronidazole or clindamycin either orally or vaginally are effective treatment.[14] However, there is a high rate of recurrence.[7]
The usual medical regimen for treatment is the antibiotic Metronidazole (500 mg twice a day, once every 12 hours) for 7 days.[15] 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.[16]
In 2009 one Cochrane review did not find probiotics useful in the treatment of BV[17] while another concluded they were effective when combined with antibiotics.[14]
Although previously considered a mere nuisance infection, untreated bacterial vaginosis may cause serious complications, such as increased susceptibility to sexually transmitted infections including HIV, and may present other complications for pregnant women.[18]
It is estimated that 1 in 3 women will develop the condition at some point in their lives.[19]
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