Bacterial Vaginosis

Bacterial vaginosis (BV) is characterised by an overgrowth of predominantly anaerobic organisms (Gardnerella vaginalis, Prevotella species, Mycoplasma hominis, Mobiluncus species) in the vagina, leading to replacement of lactobacilli and an increase in pH from less than 4.5 to as high as 7.0.¹ BV is not believed to be sexually transmitted.²

• 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 more sexual partners in a lifetime.

• 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 whiter discharge covering vaginal wall.

• Other vaginal infections, e.g. Candida, Trichomoniasis, Chlamydia, Gonorrhoea, Herpes simplex
• Other benign causes 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

• Amsel's criteria require at least 3 of the following for diagnosis:¹
  • Homogenous 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.
• Cannot use isolation of G. vaginalis as diagnostic criteria as is present in the majority of normal women.

• Advise to avoid vaginal douching, use of shower gel, and use of antiseptic agents or shampoo in the bath.
• Treatment is indicated for:
  • Non-pregnant 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 BV prior to termination of pregnancy in order to reduce risk of endometritis and pelvic inflammatory disease.¹
• Oral metronidazole, intravaginal metronidazole, oral tinidazole, or oral or intravaginal clindomycin.³
• Recommended regimes oral metronidazole 400-500 mg twice daily for 5-7 days or oral metronidazole 2 g immediately.¹
• Alternative regimens: intravaginal metronidazole gel (0.75%) once daily for 5 days, intravaginal clindamycin cream (2%) once daily for 7 days, clindamycin 300 mg twice daily for 7 days or tinidazole 2g immediately.¹
• Pregnant women can be treated with oral metronidazole or oral clindamycin in the usual way.¹
• Women who are breast feeding should be prescribed intravaginal rather than oral treatment.¹
• 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.¹
• 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 bd for 3 days at the start and end of menstruation may be effective.

• Endometritis and pelvic inflammatory disease after termination of pregnancy.
• Bacterial vaginosis can increase the risk of acquiring and transmitting HIV.²
• In continuing pregnancy, BV is associated with various complications including⁴:
• Late miscarriage
• Preterm delivery
• Premature rupture of membranes
• Low birth weight
• Postpartum endometritis

• May resolve without treatment.
• Up to 60% relapse within 3 months of successful treatment.