Bacterial Vaginosis

Overview

Bacterial vaginosis (BV) is a dysbiosis, describing an overgrowth of Gardnerella vaginalis and other anaerobic bacteria, and a decrease in lactobacilli, resulting in an increased vaginal pH and the vagina losing its normal acidity. BV is not a sexually transmitted infection, however, its prevalence is higher in sexually active people and is considered to be associated.

Epidemiology

• BV is the most common cause of abnormal vaginal discharge in people of childbearing potential
• Its prevalence is higher in sexually active people, however, it is not a sexually transmitted infection

Risk Factors

• Being sexually active
• Multiple sexual partners
• Recent change in sexual partners
• Sharing of unwashed toys
• Not using barrier protection (e.g. condoms)
• Menstruation – semen and menstruation are associated with increasing vaginal pH
• Inadequate genital hygiene, but also excessive cleaning (e.g. douching)
• Smoking

Presentation

Overview

Around 50% of people with BV are asymptomatic. Features can include:

• Abnormal vaginal discharge – described as ‘fishy-smelling’, thin, grey/white
• There is no itching, soreness, abnormal vaginal bleeding, or pelvic pain

Diagnosis

Amsel’s criteria

Amsel’s criteria can be used to diagnose BV. If 3 or more are present, BV is diagnosed:

• Presence of a homogenous grey-white discharge
• pH of vaginal fluid >4.5
• Fishy odour when potassium hydroxide 10% solution is added to the discharge on a microscope slide – a positive ‘whiff test’
• Clue cells are seen on microscopy.

Management

Overview

• Asymptomatic (e.g. picked up incidentally):
  • Not pregnant: no treatment 
  • Pregnant: discuss with obstetrician whether treatment is appropriate or not
• Symptomatic:
  • Not pregnant: oral metronidazole for 5-7 days or a single 2g dose of metronidazole
    • Alternatives include topical metronidazole or topical clindamycin
  • Pregnant: oral metronidazole 5-7 days

Complications

Recurrence is common – this may be over 50% at 12 months and may be due to a failure of the normal lactobacilli to re-establish dominance.

Obstetric complications – BV is associated with complications including preterm labour and delivery, preterm premature rupture of membranes, low birthweight, endometritis, and spontaneous abortion.

Increased risk of sexually transmitted infections – the risk of acquiring HIV is 2 times higher and people with HIV have a 3-fold increased risk of transmitting HIV. Other infections include Chlamydia, gonorrhoea, and genital herpes.