Bacterial vaginosis (BV) is caused by an overgrowth of predominantly anaerobic organisms - (Gardnerella vaginalis, Prevotella spp., Mycoplasma hominis, Mobiluncus spp.) - in the vagina. They replace lactobacilli and the pH increases from less than 4.5 to as high as 7.0. BV is not believed to be sexually transmitted (it can occur in virgins); however, sexual activity has been linked to development of the infection.¹

Epidemiology

• Reported prevalence has been reported as 5% in a group of asymptomatic college students, 12% in pregnant women attending an ante-natal clinic and 30% in women undergoing termination of pregnancy.¹
• Prevalence is higher amongst sexually active than non-sexually active women, higher in black women than white, those with an intrauterine contraceptive device, and those who smoke.¹
• BV is associated with starting intercourse at an early age and having a higher number of sexual partners in a lifetime.

Presentation

• Offensive, fishy-smelling vaginal discharge without soreness or irritation.
• Approximately half of all women infected are asymptomatic.
• On examination there is usually a thin layer of white discharge covering the vaginal wall.

Differential diagnosis

• Other vaginal infections, e.g. candida, trichomoniasis, chlamydia, gonorrhoea, herpes simplex.
• Other benign causes of vaginal discharge, e.g. physiological discharge, chemical irritants, foreign body, pregnancy, cervical ectropion.
• Tumours of the vulva, vagina, cervix, or endometrium.
• Postmenopausal vaginal discharge due to atrophic vaginitis.
• Vaginal discharge after gynaecological surgery.

Investigations

• Amsel's criteria require at least 3 of the following for diagnosis:¹
  • Homogeneous discharge as above.
  • Microscopy showing vaginal epithelial cells coated with a large number of bacilli.
  • Vaginal pH >4.5.
  • Fishy odour on adding 10% potassium hydroxide to vaginal fluid.
• Alternatively, diagnosis can be made from symptoms and swab showing large number of anaerobes with small number of lactobacilli.
• The isolation of G. vaginalis as a diagnostic criterion cannot be used, as it is present in the normal flora of the majority of women.

Management¹

• Advise avoidance of vaginal douching², use of shower gel, and use of antiseptic agents or shampoo in the bath.
• Treatment is indicated for:
  • Nonpregnant women with symptoms.
  • Women undergoing gynaecological operations.
  • Pregnant women with symptoms, a history of preterm delivery without an obvious cause, or second trimester miscarriage (even if they are asymptomatic).
  • There is evidence for the benefit of screening for and treating bacterial vaginosis (BV) prior to termination of pregnancy in order to reduce risk of endometritis and pelvic inflammatory disease.
• Recommended drugs include oral or vaginal metronidazole, or intravaginal clindamycin.³
• Recommended regimes: oral metronidazole 400-500 mg twice daily for 5-7 days or oral metronidazole 2 g immediately.
• Alternative regimens: intravaginal metronidazole gel (0.75%) once daily for 5 days, intravaginal clindamycin cream (2%) once daily for 7 days.
• Oral clindamycin 300 mg twice daily for 7 days or oral tinidazole 2 g immediately are also effective treatments.
• Pregnant women can be treated with oral metronidazole or oral clindamycin in the usual way.
• Women who are breast-feeding should be prescribed intravaginal rather than oral treatment.
• It is not necessary to have a further test to prove resolution if symptoms resolve. If treatment is prescribed in pregnancy to reduce the risk of preterm birth, a repeat test should be made after 1 month and further treatment offered if the BV has recurred.
• There is no evidence that opportunistic screening for (and treatment of) BV reduces risk of preterm birth.⁴
• There is no established treatment of recurrent BV but metronidazole gel 0.75% twice weekly for 4 to 6 months to decrease symptoms, after an initial treatment daily for 10 days, or metronidazole orally 400 mg twice daily for 3 days at the start and end of menstruation may be effective.
• There is no evidence that probiotics are effective against BV.⁵

Complications

• Endometritis and pelvic inflammatory disease after termination of pregnancy.
• Bacterial vaginosis (BV) can increase the risk of acquiring and transmitting HIV.⁶
• In pregnancy, BV is associated with various complications including:⁷
  • Late miscarriage
  • Preterm delivery
  • Premature rupture of membranes
  • Low birthweight
  • Postpartum endometritis

Prognosis

• It may resolve without treatment.
• Up to 60% of patients have a relapse within 3 months of successful treatment.

Document references

1. Management of bacterial vaginosis, British Association for Sexual Health and HIV (2006)
2. Brotman RM, Ghanem KG, Klebanoff MA, et al; The effect of vaginal douching cessation on bacterial vaginosis: a pilot study. Am J Obstet Gynecol. 2008 Jun;198(6):628.e1-7. Epub 2008 Mar 4. [abstract]
3. Ugwumadu A, Manyonda I, Reid F, et al; Effect of early oral clindamycin on late miscarriage and preterm delivery in asymptomatic women with abnormal vaginal flora and bacterial vaginosis: a randomised controlled trial. Lancet. 2003 Mar 22;361(9362):983-8. [abstract]
4. McDonald HM, Brocklehurst P, Gordon A; Antibiotics for treating bacterial vaginosis in pregnancy. Cochrane Database Syst Rev. 2007 Jan 24;(1):CD000262. [abstract]
5. Senok AC, Verstraelen H, Temmerman M, et al; Probiotics for the treatment of bacterial vaginosis. Cochrane Database Syst Rev. 2009 Oct 7;(4):CD006289. [abstract]
6. Bacterial vaginosis, Clinical Knowledge Summaries (April 2009)
7. Oakeshott P, Hay P, Hay S, et al; Association between bacterial vaginosis or chlamydial infection and miscarriage before 16 weeks' gestation: prospective community based cohort study. BMJ. 2002 Dec 7;325(7376):1334. [abstract]

Internet and further reading

• Vaginal discharge - guideline for primary care, Health Protection Agency (October 2009); Quick reference guide for primary care
• Vaginal discharge, Clinical Knowledge Summaries (January 2009)
• Curran D; Bacterial Vaginosis, eMedicine, Sep 2010

Acknowledgements