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Bacterial Vaginosis (BV)

BASHH Bacterial Vaginosis. Last updated: Dec 2012. NICE CKS Bacterial vaginosis. Last revised: Jul 2023.

Background Information

BV is the commonest cause of abnormal discharge in women of childbearing age.

Overgrowth of
  • Gardenerella vaginalis and other anaerobic bacteria

Seen almost exclusively in sexually active women
  • Vaginal douching
  • Receptive cunnilingus (oral sex)
  • Black race
  • Recent change of sex partner
  • Smoking
  • Presence of an STI e.g. chlamydia or herpes

Typical symptoms:
  • ~50% are asymptomatic
  • Offensive fishy smelling vaginal discharge

Signs:
  • Thin, white, homogeneous discharge
  • Coating the vagina and vestibule walls
 
 

BV is not usually associated with signs of inflammation e.g. irritation, itching, soreness.

Guidelines

There are 2 main approaches recommended by BASHH. Also see the NICE CKS recommendation.

BV is diagnosed if 3 out of 4 are present:
  • Thin, white, homogenous discharge
  • Clue cells present (on micorscopy)
  • Vaginal fluid pH >4.5
  • Release of fishy odour upon adding KOH (Whiff test)

The Hay/Ison criteria to be used with gram stained vaginal smear:

  • Grade 1 (Normal): Lactobacillus morphotypes predominate
  • Grade 2 (Intermediate): mixed flora with some Lactobacilli present, but Gardnerella or Mobiluncus morphotypes also present
  • Grade 3 (BV): predominantly Gardnerella and/or Mobiluncus morphotypes. Few or absent Lactobacilli
 

Additional grades which have not been correlated with clinical features:

  • grade 0: no bacteria present
  • grade 4: gram +ve cocci predominate

Diagnosis can be made if:
  • Typical clinical symtpoms + no itch or soreness
  • Vaginal pH >4.5 

There is no need for a swab for microscopy and/or culture if the above is met. If testing of pH cannot be performed or there is diagnostic doubt

 

Points regarding taking discharge sample:

  • Roll the swab anywhere on the vaginal wall to obtain a sample
  • AVOID collecting the sample from the cervix (where has alkaline secretions) and the posterior vaginal fornix (where cervical secretions can collect)
  • To test the pH: rub the discharge onto a narrow-range pH paper (urine pH dipsticks are NOT suitable)

Note that a vaginal discharge pH >4.5 is suggestive of, but NOT specific to DV.

Trichomoniasis is another recognised cause of raised vaginal pH. 

Advise to avoid the risk factors:
  • Stop smoking
  • Avoid vaginal douching
  • Avoid use of antiseptics / bubble baths / shampoos in the bath
 

Vaginal douching and bubble baths are discouraged because they disrupt the normal lactobacillus‑dominated flora and raise vaginal pH, creating an environment that allows overgrowth of BV‑associated anaerobes.

Treatment is only indicated if symptomatic.

1st line regimen (any):
  • Oral metronidazole 400mg BD for 5-7 days
  • If adherence to treatment is an issue → oral metronidazole 2g single dose
  • If prefer topical treatment / cannot tolerate oral treatment → intravaginal metronidazole gel / clindamycin cream 

2nd line:
  • Oral clindamycin
  • Oral tinidazole
 
 

Note that alcohol interacts with BOTH oral and topical metronidazole.

Similar to treatment in non-pregnant individuals:

  • Treatment only indicated in sympotmatic individuals
  • 1st line: oral metronidazole 400mg BD for 5-7 days

Important: avoid oral metronidazole 2g single dose in pregnancy.

Test of cure is not required if symptoms resolve.

References

Author: Adams Lau
Reviewer:
Last edited: 03/05/25