Bacterial vaginosis

Bacterial vaginosis
Classification & external resources

ICD-10	B96., N76.
ICD-9	616.1
MeSH	D016585

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 occurring bacterial flora, and should not be confused with yeast infection (candidiasis), or infection with Trichomonas vaginalis (trichomoniasis) which are not caused by bacteria.

Contents 1 Symptoms and signs 2 Diagnosis 2.1 In clinical practice 3 Causes 4 Complications 5 Treatment 6 References

Symptoms and signs

The most common symptom of BV is an abnormal vaginal discharge (especially after sex) with an unpleasant fishy and often tuna-like 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 the menstrual cycle - a normal discharge is at its clearest about 2 weeks before the period starts.

Diagnosis

A healthcare professional seeing a woman presenting with questions about vaginal discharge will have several diagnoses in mind to account for it. These may include:

• The discharge is normal for the woman
• 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 healthcare provider 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 the 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]

In clinical practice

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.	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)
Score 0 for >30 Score 1 for 15–30 Score 2 for 14 Score 3 for <1 (this is an average, so results can be >0, yet <1) Score 4 for 0	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	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.

Causes

A healthy vagina normally contains many microorganisms, some of the common ones are Lactobacillus crispatus and Lactobacillus jensenii. Lactobacillus, particularly hydrogen peroxide-producing species, appears to help prevent other vaginal microorganisms from multiplying to a level where they cause symptoms. (Note: Lactobacillus acidophilus is not one of the species of Lactobacillus identified as playing a protective role in vaginal flora.) 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. In turn these produce toxins which affect the body's natural defenses and make re-colonization 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 may provide some protection and there is no evidence that spermicide increases BV risk. Although BV appears to be associated with sexual activity, 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.

Complications

Although previously considered a mere nuisance infection, untreated bacterial vaginosis may cause serious complications, such as increased succeptibility to sexually transmitted infections including HIV, and may present other complications for pregnant women.^[7] It has also been associated with an increase in the development of Pelvic inflammatory disease (PID) following surgical procedures such as a hysterectomy or an abortion.

Treatment

Bacterial vaginosis can be cured by antibiotics such as metronidazole and clindamycin. However, there is a high rate of recurrence.^[6] Currently, there are very few over the counter products that address bacterial vaginosis. A vaginal gel product called RepHresh claims to regulate the pH level. Boric acid capsules inserted vaginally is considered a home treatment. Lactobacillus supplements may also be used; Fem-dophilus (Jarrow Formulas) is a lactobacillus product which specifically claims to help maintain healthy vaginal flora.^[8] It should be noted that seeking medical attention is often necessary, because none of the over the counter products can claim to treat an active infection. More importantly, patients often inaccurately diagnose BV as a yeast infection, and delay proper treatment which may lead to complications. In a randomized controlled trial,^[9] 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 vaginal metronidazole gel was associated with fewer gastrointestinal complaints.

References