Bacterial vaginosis: diagnosis and management

Introduction

Bacterial vaginosis (BV) is a common vaginal infection caused by an overgrowth of bacteria in the vagina, resulting in a change in the normal vaginal microbiota​[1]​. This imbalance can cause symptoms such as vaginal discharge, odour and itching. BV is not considered a sexually transmitted infection (STI), but sexual activity can increase the risk of developing BV. Other risk factors include vaginal douching and hormonal changes​[2]​.

In the UK, BV is estimated to affect 15–30% of women of reproductive age, making it one of the most common vaginal infections​[1,3]​. BV is often misdiagnosed or left untreated, which can lead to complications, such as pelvic inflammatory disease (PID), increased risk of STIs and adverse pregnancy outcomes, including preterm labour and low birth weight​[4–8]​.

Pharmacists play an essential role in the management of BV by identifying the condition, providing advice on self-care and signposting patients to medical care at early stages. Additionally, pharmacists can recommend and supply appropriate treatment options, such as antibiotics, to women with confirmed BV diagnosis or recurrent infections.

Symptoms

Approximately 50% of females who get BV are asymptomatic​[4]​. Symptoms include an offensive, fishy-smelling vaginal discharge that can be thin, white and homogeneous, coating the walls of the vagina and vestibule. BV is not usually associated with soreness, itching or irritation​[1,3]​.

Risk factors

Some of the risk factors that can increase the likelihood of developing BV include being sexually active; certain sexual practices, such as receptive cunnilingus; or having concurrent STIs​[1,3]​.

Vaginal pH in a female of child-bearing age is usually 3.5–4.5, changes in pH can result in changes in the normal vaginal flora. Therefore, things that increase vaginal pH increase the risk of BV, such as:

• Vaginal douching, which disrupts the natural balance of bacteria in the vagina;
• The use of antiseptics, bubble baths or shampoos in the bath;
• Menstruation;
• Presence of semen in vagina;
• Ethnicity — BV is more prevalent in black women;
• Use of copper intrauterine devices​[1,3,4]​.

Smoking disrupts the natural balance of bacteria in the vagina and increases risk of developing BV; however, there is insufficient data to suggest that stopping smoking reduces the risk​[9]​.

Diagnosis

Patients with symptoms suggestive of BV present to a broad number of healthcare settings, including community pharmacies, general practice and integrated sexual health clinics. The availability of diagnostics in these settings varies from syndromic to microscopic, and while stratification of diagnostics might provide more directed treatment, restricting the number of settings woman have access to that are able to make a diagnosis of BV may result in healthcare inequity.

History taking is a vital aspect of BV diagnosis, but it can be difficult to differentiate between BV, candida and STIs, including trichomonas vaginalis​[1]​. A good history should include a timeline of symptoms, including any change in vaginal discharge, with additional descriptive factors, such as quantity, quality, odour and colour. Symptom patterns should be elicited, including the relationship of symptoms to menstruation and sexual intercourse​[1]​. Women should also be assessed for systemic or concerning features, including pain and fever; if present, patients should be referred on to a medical practitioner.

In GUM or integrated sexual health clinics, the diagnosis of BV follows British Association for Sexual Health and HIV (BASHH) guidelines​[1]​. Vaginal smears are Gram stained and viewed under light microscopy. The Hay/Ison criteria are used to grade microscopic findings from one to three, based on the morphologic appearance of vaginal lactobacilli and the presence or absence of Gardnerella and/or Mobiluncus morphotypes​[1]​. UK guidance favours this over the Amsel criteria, which combine symptomatic presentation, wet microscopy findings and near-patient pH and KOH testing (for fungal infection)​[1]​.  

Women undergoing testing for BV, who are sexually active, should undergo testing for STIs, including chlamydia, gonorrhoea and trichomonas, to rule out additional causes for their symptoms​[1]​.

For women with recurrent symptoms, keeping a symptom diary can be helpful to spot any physiological patterns or additional triggers.

While over-the-counter testing strips are available, most of these tests are based on pH litmus strips, with little clinical evaluation to support their use.

Management

Treatment is indicated for symptomatic women and women undergoing gynaecological surgical or invasive diagnostic procedures​[1,3]​. Guidelines from the National Institute for Health and Care Excellence and BASHH recommend the use of topical or oral metronidazole or clindamycin as first-line treatments for BV​[1,3]​.

Patients prescribed metronidazole first line should take 400mg twice daily for 5–7 days​[1,3]​. Oral treatment is well tolerated and cost-effective, with cure rates of 70–80%​[1]​. Alternatively, metronidazole 2g can be taken as a single dose to support adherence. Metronidazole should be used with caution in patients with severe liver disease or hepatic encephalopathy; these patients should take a third of the daily dose once daily​[3,10]​.

Pharmacists should be aware of the following interactions:

• Metronidazole interacts with alcohol, causing individuals to experience a disulfiram-like reaction (flushing, increased respiratory rate, increased pulse rate, nausea, headache and dizziness); therefore, patients should avoid drinking alcohol during treatment and for at least 48 hours afterwards;
• The anticoagulant effects of warfarin and acenocoumarol can be markedly increased by metronidazole. The patient’s international normalised ratio (INR) should be monitored for concomitant use. Patients should be counselled on signs of unexplained bleeding;
• It has been reported that metronidazole may increase the concentration of lithium, leading to renal damage. Concurrent use should be avoided or with close monitoring and potential dose adjustment​[10]​.

Topical metronidazole can be used if the patient cannot tolerate oral metronidazole or prefers local therapy. Intravaginal metronidazole 0.75% gel should be applied once per day for 5 days​[1,3]​. This is off-label for women aged younger than 18 years​[11]​. Common side effects include dry skin, erythema and skin irritation. Treated sites should avoid exposure to ultraviolet light or strong sunlight. Drug interactions with topical treatments are unlikely owing to lack of systemic absorption; however, very rare cases of altered INR after topical treatment in patients taking warfarin and other coumarin anticoagulants have been reported, so cautions should be exercised​[11]​.

The alternate first-line treatment for BV is clindamycin. While clindamycin shows better activity against Gardnerella vaginalis and Mycobacteria hominis than metronidazole, it also impacts vaginal lactobaccili​[12]​. Intravaginal clindamycin 2% cream should be applied once daily for 7 days. Common side effects include cervicitis, vaginal candidiasis, vulvovaginal irritation and vaginal discharge​[3,13]​. The cream can damage latex condoms and diaphragms; therefore, women should not rely on barrier methods of contraception during treatment and for five days after​[13]​. Erythromycin should not be used concurrently as antagonism has been observed​[3]​.

Alternative regimens

Oral tinidazole and clindamycin courses could be used but these are less preferred owing to cost​[1,3]​.

Considerations in pregnant or breastfeeding women

Oral and topical metronidazole, as well as topical clindamycin, can be considered for use in pregnancy. However, high-dose metronidazole as a single dose is not recommended. Metronidazole enters breast milk and may affect its taste​[1]​. Intravaginal preparations of metronidazole or clindamycin are preferred for lactating women​[1]​.

Patient prognosis

While existing treatments are effective and the majority of acute episodes of BV will resolve, recurrence rates are high​[1]​. It is important that expected recurrence is not labelled as resistant BV or treatment failure, as this may cause unnecessary distress. Women with persistent recurrence of BV that impacts their quality of life should be referred to specialist care for elimination of alternative diagnoses (e.g. STIs) and to discuss additional treatment options, such as boric acid; however, there can be minimal access and limited data for these options.

Women with PID may have a high prevalence of BV but it does not appear to be a reliable predictor of subsequent PID. However, there is an association with endometritis and PID following termination of pregnancy in women with pre-procedural BV. In pregnancy, there is an association with late miscarriage, pre-term birth and premature rupture of membranes​[14–19]​.