What is bacterial vaginosis and what are the symptoms?
Bacterial vaginosis (BV) is a common condition of the vagina caused by an overgrowth of various bacteria (germs). It is not just a simple infection caused by one type of bacterium.
- The main symptom of BV is a vaginal discharge. BV is the most common cause of vaginal discharge in women of childbearing age. The discharge is often a white-grey colour, and often has a fishy smell. The smell may be most noticeable when having sex. The discharge tends to be heaviest just after a period, and after having sex.
- The discharge of BV does not usually cause itch or soreness around the vagina and vulva.
- Many women with BV do not have any symptoms (up to half of cases). These women may be found to have BV by chance when vaginal swabs are taken for other reasons.
Note: BV is not the only cause of a vaginal discharge. Various conditions can cause a discharge. For example, the second most common cause of a discharge is due to thrush which is an infection caused by a yeast called candida. Unlike BV, thrush typically causes a thicker white discharge which tends to cause itch and soreness around the vagina and vulva.
What causes bacterial vaginosis?
BV is not caused by a single bacterium (germ). In BV, an 'overgrowth' of various bacteria occurs in the vagina. It is not clear why this happens. Normally, there are a number of different types of harmless bacteria in the vagina. These bacteria help in the defence against harmful germs (such as candida which causes thrush). In BV, there is a change in the balance of the normal bacteria in the vagina, and certain bacteria multiply and thrive much more than usual. Some bacteria become much more prominent than they normally are.
Doctors describe these changes as " a change in the bacterial flora of the vagina from mainly lactobacillus species to high concentrations of anaerobic bacteria."
BV is not caused by poor hygiene. In fact, excessive washing of the vagina may alter the normal balance of bacteria in the vagina, which may make BV more likely to develop.
Who gets bacterial vaginosis and how common is it?
At least 1 in 10 women have BV at some time in their life. It may be much more common than this as many cases are mild and cause no symptoms. (BV is at least twice as common as vaginal thrush.) Any woman can be affected by BV. BV is more common in women who have an intra-uterine contraceptive device (IUD). One study found that about half of women using an intrauterine contraceptive device had at least one episode of BV over a two year period.
Is bacterial vaginosis a sexually transmitted disease?
No, BV can affect any woman, including those who do not have sex. No bacterium is passed on that causes this condition. Sexual partners of women with BV do not need any treatment. However, some cases of BV seem to be sexually 'related'. It may develop after a change in sexual partner. In these cases, the infection is not 'caught' from anyone. However, a change in sexual partner may affect the balance of normal bacteria in the vagina.
How is bacterial vaginosis diagnosed?
- The typical discharge, and its characteristic fishy smell, makes BV likely.
- The discharge of BV has a typical acid level (pH) compared to other causes of discharge. (The overgrowth of the bacteria of BV causes the pH to change.) In addition, if an alkali is added to a sample of the discharge, it often causes a characteristic fishy smell.
- To help clarify the diagnosis, a sample (swab) of the discharge may be sent for testing. Large numbers of various bacteria that occur with BV are seen under the microscope.
- Other tests may be done to rule out other causes of vaginal discharge.
What are the possible complications with bacterial vaginosis?
- Pregnancy. If you have untreated BV during pregnancy, you have an increased risk of developing some complications of pregnancy. For example, early labour, miscarriage, and infection of the uterus (womb) after childbirth.
- Surgery. If you have untreated BV, the chance of developing an infection of the uterus is higher following certain operations. For example, following a termination of pregnancy or a vaginal hysterectomy. However, antibiotics are given before various operations of the uterus if you have BV which usually prevent these infections.
- HIV. If you have untreated BV, you have an increased risk of developing HIV infection if you have sex with someone who is infected with HIV.
What is the treatment for bacterial vaginosis?
Metronidazole
A course of metronidazole tablets is the common treatment. It clears BV in about 7-8 in 10 cases. Read the page that comes with the tablets for a full list of possible side-effects and cautions. However, main points to note about metronidazole include:
- The usual dose is 400 mg twice a day for seven days. A single dose of 2 grams is an alternative, although this may be less effective and may cause more side-effects.
- Some people feel sick, and may vomit when they take metronidazole. This is less likely to occur if you take the tablets straight after food. A metallic taste is also a common side-effect.
- Do not drink any alcohol while taking metronidazole, and for at least 48 hours after stopping treatment. The interaction with alcohol can cause vomiting and other problems.
- Breastfeeding: metronidazole can get into breast milk, but is not thought to affect breastfed babies. However, to play safe, the standard 7-day course with the lower dose is preferred so as a baby does not get a large dose. If it is essential to use the large 2-gram single dose then it should be taken after the last breastfeed of the evening, at the start of the overnight breastfeeding break, to limit exposure to the baby.
Alternative antibiotic treatments
Metronidazole vaginal gel or clindamycin vaginal cream placed inside the vagina can be used if you prefer a topical treatment, or have unpleasant side-effects with metronidazole tablets. Note: clindamycin vaginal cream can cause weakening of condoms. Therefore, during treatment and for five days after treatment with clindamycin vaginal cream, do not rely on condoms to protect against pregnancy and sexually transmitted diseases.
Not treating is an option if you are not pregnant
BV often causes no symptoms or the symptoms are mild. Also, there is a good chance that BV will gradually clear without treatment, as the balance of bacteria in the vagina may correct itself. However, if you are pregnant you will usually be advised to take antibiotic treatment to prevent the increased risks during pregnancy if you have BV (described above).
Treating recurrences
BV recurs within three months in about half of women who have been successfully treated. If it does recur, a repeat course of antibiotics will usually be successful. A small number of women have repeated episodes of BV, and need repeated courses of antibiotics.
How can I prevent further episodes of bacterial vaginosis?
Most episodes of BV occur for no apparent reason, and cannot be prevented. However, the following are thought to help prevent some episodes of BV. The logic behind these tips is to try not to upset the normal balance of bacteria in the vagina.
- Do not push water into your vagina to clean it (douching).
- Do not add bath oils, detergents, bubble bath, etc, to bath water.
- Do not wash around your vagina too often. Once a day is usually enough.
©EMIS and PIP 2005
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