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| Bacterial vaginosis |
11-Jul-2007 |
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WOMEN
’
S HEALTH: An increase in the number of anaerobic bacteria in the vagina upsets the pH balance of this normally acidic environment. By Dr Terri Foran
IN the normal healthy vagina, large numbers of lactobacilli are present. These aerobic bacteria produce lactic acid and a small amount of hydrogen peroxide, which keep the vaginal environment acidic. The pH of the vagina during the reproductive years is normally between 3.8 and 4.2.
For reasons that are not fully understood, the vaginal ecosystem changes in women with bacterial vaginosis, so that a mix of anaerobic flora proliferate. These may include organisms such as Gardnerella vaginalis, Mycoplasma hominis, Mobiluncus bacteroides and Prevotella, with concentrations of these bacteria increasing up to 1000-fold from the usual levels. There is also another bacteria called Atopobium vaginaliswhich appears to be associated with a higher incidence of rapid relapses after treatment and more frequent recurrences.
Bacterial vaginosis, commonly referred to as BV, has had various other names in the past, such as non-specific vaginitis, haemophilus vaginitis and gardnerella vaginitis. In women with bacterial vaginosis, the pH of the vagina increases to more than 4.5. This rise in pH further compromises the survival of any remaining lactobacilli.
What are the usual
symptoms?
Typically, women will present to their doctor with a vaginal discharge that is often more noticeable in the latter half of the menstrual cycle. Some women find their discharge is heavier than usual, leading to annoying vulval wetness and mild irritation.
The discharge is usually a pearly grey/white colour and has the consistency of milk. Commonly, women will complain of an unpleasant strong fishy odour or even a slight ‘bubbling’ sensation. These symptoms are due to the amines produced by the anaerobic bacteria. The odour is often more obvious after unprotected sex because semen, which is relatively alkaline, increases the amine release. Some women may say their sexual partner had noticed the change in vaginal odour, but they had not noticed any difference.
In about 50% of women with clinical bacterial vaginosis, there are no or minimal symptoms and the condition is diagnosed incidentally during a Pap test or other routine gynaecological examination.
How common is it?
Bacterial vaginosis is the most prevalent form of vaginal disturbance in women of reproductive age. It is much more common, for example, than monilial vaginitis. The average incidence varies from 10% to 35% in a population of gynaecology inpatients to up to 60% in women attending a sexual health service.
Factors that increase the risk of bacterial vaginosis are lower socioeconomic status, multiple sexual partners, the presence of an intrauterine device and having sex with other women. Regular douching also appears to increase the risk of bacterial vaginosis, but this practice is relatively uncommon in Australia. Interestingly, bacterial vaginosis is more common in African and Afro-American women, who have a slightly higher average vaginal pH than Caucasian and Asian women.
Is it sexually transmitted?
There may be an indirect association between bacterial vaginosis and sexual activity. Bacterial vaginosis is more common in women who have had more than three sexual partners (male or female) in the preceding 12 months. Antibiotic treatment of the partner does not improve the rate of cure or reduce the chance of recurrence and there is no place for routine treatment of an asymptomatic partner.
One theory is that there may be as yet unidentified factors transmitted in semen, vaginal secretions or even saliva, which can trigger an alteration in the vaginal microflora in susceptible women, which then becomes self-perpetuating. Certainly anecdotally, there also seems to be an association with times of stress or significant change in the woman’s life.
Why is bacterial vaginosis
important?
For most women, bacterial vaginosis is simply an annoying and slightly embarrassing condition. When picked up coincidentally, the advice is to simply ask if the woman has noticed a change in her normal vaginal discharge and treat her if the answer is yes.
If likely bacterial vaginosis is reported on a Pap test report and the condition was not clinically obvious at the time of examination, there is usually no need to recall the patient for treatment. However, there are some circumstances when the presence of bacterial vaginosis is associated with the potential for serious complications. These include:
* During pregnancy. Bacterial vaginosis is associated with an increased risk of miscarriage, premature rupture of the membranes, chorioamnionitis, preterm delivery and post-partum endometritis. Unfortunately, it is uncertain whether even prompt treatment of the condition significantly reduces the risk of preterm delivery.1
* Gynaecological surgery
and instrumentation. Endometritis and pelvic infection are more common when caesarean section, termination of a pregnancy or insertion of an intrauterine device is performed in a woman with bacterial vaginosis. Women with known bacterial vaginosis should receive appropriate antibiotic cover at the time of such procedures.
How is the diagnosis
made?
The diagnosis of bacterial vaginosis is often suspected by the clinician before examination on the basis of the symptoms described by the woman. With the easy availability of oral and vaginal anti-candida treatment, most women will have used these and failed to get relief from their symptoms before they present to their doctor.
Examination will usually reveal an increased amount of discharge at the introitus and within the vagina. The discharge is characteristically thin, milky and grey-white in colour, and small bubbles may be apparent in the posterior vaginal pool.
If a microbiological swab is to be sent for pathology, it should be obtained from the vagina and not from the cervix. Once removed from the vagina, the speculum should be discreetly checked for the distinctive fishy odour (the so-called ‘whiff test’).
Amsel
’
s criteria
Pending microbiological diagnosis, the diagnosis can be made by means of Amsel’s criteria. Bacterial vaginosis can be diagnosed when three out of the four following findings are present:
* Presence of homogeneous vaginal discharge.
* Vaginal fluid with a pH of more than 4.5.
* Positive amine test (this involves mixing a drop of dilute potassium hydroxide with the discharge and checking for intensification of the amine odour).
* Detection of clue cells on microscopic examination. Clue cells are simply vaginal epithelial cells that have been coated with masses of adherent bacteria, usually coccobacteria. The slide is prepared by placing a drop of normal saline on the discharge, placing a cover slip over the top and examining it with a basic light microscope.
The reality is that few practices these days have ready access to a light microscope or the materials needed to prepare slides or amine tests. The whiff test can act as a de facto amine test, but the ability to quickly determine that the vaginal pH is more than 4.5 by means of a simple pH test strip must rank as one of the most useful office tests for those with a significant women’s health component to their clinical practice.2,3
How is bacterial
vaginosis best treated?
The most common initial treatment for bacterial vaginosis in Australia is a single 2g dose of either metronidazole or tinidazole. This will settle symptoms in about 70% of women. In resistant cases, a longer course of treatment may be necessary, usually metronidazole 200mg tds for seven days. Different regimens are used in other countries. For example, in the US the recommended dose of metronidazole is 500mg bd for one week.
Allergies to these drugs are rare but side effects unfortunately are not and many women will experience nausea for the duration of treatment. This nausea is increased markedly if there is any concurrent alcohol consumption and women should be warned to avoid any alcohol until the course is completed. Another common unpleasant side effect is a bitter metallic after-taste, which tends to become persistent with longer courses of treatment.
Tinidazole is classified as a B3 medication and its use should be avoided in pregnancy. Metronidazole is classified as a B2 and although it has been more widely used in pregnancy most clinicians still advise that its use be avoided if possible in the first trimester. In some countries a metronidazole vaginal gel is available and has tended to supplant the use of oral medications since it has a much lower incidence of side effects. Unfortunately, such a preparation is not available in Australia.
An alternative pharmaceutical treatment is a vaginal cream of clindamycin 2%, which is often the treatment of choice during pregnancy and when women have experienced significant side effects during previous treatment with metronidazole. Unfortunately, clindamycin is a relatively expensive option and although it is effective at eliminating the anaerobic bacteria responsible for bacterial vaginosis it also targets the local lactobacilli, increasing the potential for early recurrence. For similar reasons, there is also no real place for the use of broad-spectrum antibiotics, such as the synthetic penicillins and cephalosporins, in the treatment of bacterial vaginosis, although they may be listed on the sensitivity report from the pathologist.
Some women, particularly those with recurrent symptoms, are keen to explore non-pharmacological treatments for bacterial vaginosis. One alternative has been to attempt to re-acidify the vagina by means of a week-long course of a commercial preparation such as Aci-Jel or a dilute cider vinegar douche. There is minimal good scientific evidence to support this practice, although there has been one recent study that demonstrated the use of maintenance acidic vaginal gel after treatment with metronidazole doubled the time taken to recurrence and significantly reduced the overall recurrence rate.4
Another strategy has been to try to re-colonise the vagina with compatible lactobacilli in an attempt to restore the normal acid balance. There are several vaginal lactobacilli preparations available, the most widely promoted in Australia being EcoVag. This is a seven-day course of vaginal capsules containing two different lactobacilli, Lactobacillus
gasseri and Lactobacillus
rhamnosus. There are a large number of scientific papers that have examined the usefulness of such an approach but they are very difficult to translate into any clinical advice because doses and duration of treatment are rarely specified and the results are contradictory.
Another problem is that there are literally hundreds of different lactobacillus species, all with slightly different properties. This means that although several different combinations of various lactobacilli species have been trialled and shown to have some efficacy, these do not always correspond to the species present in the commercial preparations. However, vaginal lactobacilli capsules appear to have few side effects and there are certainly going to be women who wish to explore these as an option for treatment or as maintenance therapy.
In view of the association with stress, particularly where the condition is recurrent, it may also be worth exploring lifestyle strategies designed to improve general heath and reduce life stressors.
Conclusion
In many ways bacterial vaginosis remains a mystery. For most women it is a self-limiting infection that is a nuisance, but for others it can have a profound impact on their reproductive health. All clinicians should be aware of the symptoms and be able to differentiate them from other common vaginal infections, such as thrush.
It would be useful if clinicians in Australia had access to a dedicated vaginal metronidazole preparation because there seems little doubt this would be the initial treatment of choice for most women were it available in Australia.
Dr Foran is a sexual health
physician and co-ordinator of
the undergraduate course in
women
’
s health at the
University
of
NSW
.
References
1. Okun N, et al. Antibiotics for bacterial vaginosis or Trichomonas vaginalis in pregnancy: a systematic review. Obstetrics and
Gynecology 2005; 105(4):857-68.
2. Nyirjesy P, Sobel JD. Advances in diagnosing vaginitis: development of a new algorithm. Current
Infectious Disease Reports2005; 7(6);458-62.
3. Pauletic AJ, et al. Experience with routine vaginal pH testing in a family practice setting. Infectious
Diseases in Obstetrics and
Gynecology 2004; 12(2):63-68.
4. Wilson JD, et al. Recurrent bacterial vaginosis: the use of maintenance acidic vaginal gel following treatment. International Journal of STD
& AIDS 2005; 16(11):736-38.
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