Bacterial vaginosis
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| ICD-10 | B96., N76. |
|---|---|
| ICD-9 | 616.1 |
Bacterial vaginosis (BV) is the most common cause of vaginal infection (vaginitis). For grammatical reasons, some people prefer to call it vaginal bacteriosis. It is NOT generally considered to be a sexually transmitted infection[1] (see causes below). BV is caused by an imbalance of naturally occuring bacterial flora, and should not be confused with yeast infection (candidiasis), or infection with Trichomonas vaginalis (trichomoniasis) which are not caused by bacteria.
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[edit] Symptoms and signs
The most common symptom of BV is an abnormal vaginal discharge (especially after sex) with an unpleasant fishy smell. There is rarely itching.
Nearly half of all women with BV don't notice any symptoms.
By contrast, a 'normal' discharge will be odourless and will vary in consistency and amount with your menstrual cycle - a normal discharge is at its clearest about 2 weeks before your period starts.
[edit] Diagnosis: A Patient's Guide
When you go to your doctor with questions about vaginal discharge, he or she will have several diagnoses in mind to account for it. These may include:
- The discharge is normal for you
- Candidiasis (thrush, or a yeast infection)
- Trichomonas vaginalis (trichomoniasis)
- Bacterial vaginosis
To find out which of these is the case, a few simple tests are done. The doctor will carry out a speculum examination and take some swabs from high in the vagina. These swabs will be tested for:
- A characteristic smell—this is called the whiff test. A small amount of an alkali is added to a microscope slide that has been swabbed with the discharge—a 'fishy' odour is a positive result for bacterial vaginosis.
- Loss of acidity—the vagina is normally slightly acidic (with a pH of 3.8–4.2), which helps to control bacteria. A swab of the discharge is put onto litmus paper to check the acidity. A positive result for bacterial vaginosis would be a pH of over 4.5.
- 'Clue cells'—so called because they give a clue to the reason behind the discharge. These are epithelial cells (like skin) that are coated with bacteria. They can be seen under microscopic examination of your discharge.
Two positive results in addition to the discharge itself are enough to diagnose BV. If there is no discharge, then all 3 criteria are needed.[2]
[edit] Diagnosis: A Guide for Health Professionals
In clinical practice bacterial vaginosis (BV) is diagnosed using the Amsel criteria:[2]
1. Thin, white, yellow, homogeneous discharge
2. Clue cells on microscopy
3. pH of vaginal fluid >4.5
4. Release of a fishy odor on adding alkali—10% potassium hydroxide (KOH) solution.
At least three of the four criteria should be present for a confirmed diagnosis.[1]
An alternative is to use a Gram stained vaginal smear, with the Hay/Ison[3] criteria or the Nugent[4] criteria. The Hay/Ison criteria are defined as follows: [1]
- Grade 1 (Normal): Lactobacillus 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 standard for research are the Nugent[4] Criteria. In this scale a score of 0-10 is generated from combining three other scores. It is time consuming and requires trained staff but is has high interobserver reliability:
- 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.
- Score 0 for >30
- Score 1 for 5–30
- Score 2 for 14
- Score 3 for <1 (this is an average, so results can be >0, yet <1)
- Score 4 for 0
Gardnerella / Bacteroides morphotypes — average per high powered (1000× oil immersion) field. View multiple fields.
- Score 0 for 0
- Score 1 for <1 (this is an average, so results can be >0, yet <1)
- Score 2 for 1–4
- Score 3 for 5–30
- Score 4 for >30
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)
- Score 0 for 0
- Score 1 for <5
- Score 2 for 5+
A recent study [5] 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.
[edit] Causes
A healthy vagina normally contains many microorganisms, one of the common ones being Lactobacillus acidophilus. Lactobacillus appears to help prevent other vaginal microorganisms from multiplying to a level where they cause symptoms. The microorganisms involved in BV include Gardnerella vaginalis, Mobiluncus, Bacteroides, and Mycoplasma. In general reduction in the normal bacterial flora, because of antibiotics or PH inbalance, allows more resistant bacteria to gain a foothold and multiply; in turn these produce toxins which effect the body's natural defences and make recolonization of healthy bacteria more difficult.
Most cases of bacterial vaginosis occur in sexually active women between the ages of 15 and 44, especially after contact with a new partner. Condoms do not appear to provide protection, but use of spermicides increases BV risk somewhat. Although BV appears to be associated with and triggered by sexual intercourse, there is no clear evidence of sexual transmission.[6] 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 does not usually 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.
[edit] Treatment
Bacterial vaginosis can be cured by antibiotics such as metronidazole and tetracycline; there is however a high rate of recurrence.[6]
Bacterial vaginosis can also be treated with over the counter products such as RePhresh, boric acid, or Lactobacillus Acidophilus capsules.
In a randomized controlled trial [7], researchers found the efficacy of 0.75% metronidazole vaginal gel in treating bacterial vaginosis (cure rate 70.7%) was equivalent to that of standard oral metronidazole treatment (cure rate 71%). Treatment with oral metronidazole was associated with fewer gastrointestinal complaints.
[edit] See also
[edit] References
- ^ a b c Guideline Clearing House. "2002 national guideline for the management of bacterial vaginosis".
- ^ a b Amsel, R; PA Totten & CA Spiegel et al. (1983), "Nonspecific vaginitis. Diagnostic criteria and microbial and epidemiologic associations", Am J Med 74: 14–22
- ^ Ison, CA & PE Hay (2002), "Validation of a simplified grading of Gram stained vaginal smears for use in genitourinary medicine clinics", Sex Transm Infect 78: 413–415
- ^ a b Nugent, R. P., M. A. Krohn, and S. L. Hillier (1991). "Reliability of diagnosing bacterial vaginosis is improved by a standardized method of Gram stain interpretation". J. Clin. Microbiol 29: 297–301.
- ^ PMID 17078859
- ^ a b Bradshaw CS, Morton AN, Hocking J, et al. (2006). "High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy and factors associated with recurrence". J Infect Dis 193 (11): 1478–86.
- ^ PMID 11127100
