Levels of evidence (I-IV) and grades of recommendation (A-C) are defined at the end of the "Major Recommendations" field.
Diagnosis
Two approaches are available:
- Amsel criteria. At least three of the four criteria are present for the diagnosis to be confirmed.
- Thin, white, homogeneous discharge
- Clue cells on microscopy of wet mount
- pH of vaginal fluid >4.5
- Release of a fishy odour on adding alkali (10% potassium hydroxide [KOH])
- A Gram stained vaginal smear, evaluated with the Hay/Ison criteria or the Nugent criteria.
The Hay/Ison criteria are defined as follows:
Grade 1 (Normal): Lactobacillus morphotypes predominate
Grade 2 (Intermediate): Mixed flora with some Lactobacilli present, but Gardnerella or Mobiluncus morphotypes also present
Grade 3 (bacterial vaginosis [BV]): Predominantly Gardnerella and/or Mobiluncus morphotypes. Few or absent Lactobacilli
The Nugent score is derived from estimating the relative proportions of bacterial morphotypes to give a score between 0 and 10. A score of <4 is normal, 4 to 6 is intermediate, and >6 is BV.
The Bacterial Special Interest group of British Association for Sexual Health and HIV (BASHH) recommend using the Hay/Ison criteria in Genitourinary medicine clinics (C).
Management
General Advice
Patients should be advised to avoid vaginal douching, use of shower gel, and use of antiseptic agents or shampoo in the bath (C).
Treatment
Treatment is indicated for:
- Symptomatic women (A)
- Women undergoing some surgical procedures (A)
Women who do not volunteer symptoms may elect to take treatment if offered. They may report a beneficial change in their discharge following treatment.
Recommended Regimens
- Metronidazole 400-500 mg twice daily for 5-7 days (A)
or
- Metronidazole 2 g single dose (A)
Alternative Regimens
- Intravaginal metronidazole gel (0.75%) once daily for 5 days (A)
or
- Intravaginal clindamycin cream (2%) once daily for 7 days (A)
or
- Clindamycin 300 mg twice daily for 7 days (A)
or
- Tinidazole 2 g single dose (A)
Caution
- With metronidazole treatment alcohol should be avoided because of the possibility of a disulfiram-like action. There are no data on the risks from consuming alcohol with intravaginal metronidazole gel, but it is not recommended at present.
- Clindamycin cream can weaken condoms, which should not be used during such treatment. Pseudomembranous colitis has been reported with both oral clindamycin and clindamycin cream.
Allergy
Allergy to metronidazole is uncommon. Use 2% clindamycin cream for metronidazole allergic women.
Pregnancy and Breast Feeding
The results of clinical trials investigating the value of screening for and treating bacterial vaginosis in pregnancy have been conflicting. It is therefore difficult to make firm recommendations. A detailed discussion of trials in pregnancy is in the appendix of the original guideline document. In conclusion:
- Symptomatic pregnant women should be treated in the usual way (B).
- There is insufficient evidence to recommend routine treatment of asymptomatic pregnant women who attend a genitourinary (G-U) clinic and are found to have bacterial vaginosis.
- Metronidazole enters breast milk and may affect its taste. The manufacturers recommend avoiding high doses if breast feeding. Small amounts of clindamycin enter breast milk. It is prudent therefore to use an intravaginal treatment for lactating women (C).
Termination of Pregnancy (TOP)
Three studies have investigated whether antibiotics can reduce the rate of infectious morbidity in women with BV, following termination of pregnancy. A Scandinavian study of 231 women demonstrated a reduction in post-TOP infection by treating BV with oral metronidazole before termination (Ib). Another demonstrated a reduction in infective complications following the use of clindamycin cream (Ib). A United Kingdom study of 273 women again found a reduction in post-operative upper genital tract infection from 16% to 8.5%, but did not quite reach statistical significance. There are no data on the effectiveness of treatment administered at the time of TOP.
- These studies support screening for and treating BV with either metronidazole or clindamycin cream, to reduce the incidence of subsequent endometritis and pelvic inflammatory disease (PID) (Ia).
Sexual Partners
- No reduction in relapse rate was reported from two studies in which male partners of women with bacterial vaginosis were treated with metronidazole, one study of tinidazole, and one of clindamycin (Ib). Routine screening and treatment of male partners are therefore not indicated.
- Two studies reported a high incidence of bacterial vaginosis in female partners of lesbian women with bacterial vaginosis (II). No study has investigated the value of treating partners of lesbian women simultaneously.
Follow Up
A test of cure is not required if symptoms resolve.
Recurrent Bacterial Vaginosis
There are few published studies evaluating the optimal approach to women with frequent recurrences of BV. Possible approaches are as follows:
- Suppressive therapy. Metronidazole gel 0.75%. twice weekly for 4 to 6 months to decrease symptoms, after an initial treatment daily for 10 days, is being evaluated.
- Metronidazole orally 400 mg twice a day (bd) for 3 days at the start and end of menstruation, combined with fluconazole 150 mg as a single dose if there is a history of candidiasis also (III).
- A recent observational study reported that acigel used at the time of menstruation and following unprotected sexual intercourse was associated with a reduction in relapse rate following a course of metronidazole (III).
- Small studies of live yoghurt or Lactobacillus acidophilus have not demonstrated benefit (IIa).
- Other treatments being studied at present include the use of combinations of antibiotics with probiotic therapy and hydrogen peroxide.
Definitions:
Levels of Evidence
Ia: Evidence obtained from meta-analysis of randomised controlled trials
Ib: Evidence obtained from at least one randomised controlled trial
IIa: Evidence obtained from at least one well designed controlled study without randomisation
IIb: Evidence obtained from at least one other type of well designed quasi-experimental study
III: Evidence obtained from well designed non-experimental descriptive studies such as comparative studies, correlation studies, and case control studies
IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities
Grades of Recommendation
A (Evidence Levels Ia, Ib)
- Requires at least one randomised controlled trial as part of the body of literature of overall good quality and consistency addressing the specific recommendation.
B (Evidence Levels IIa, IIb, III)
- Requires availability of well conducted clinical studies but no randomised clinical trials on the topic of recommendation.
C (Evidence Level IV)
- Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities.
- Indicates absence of directly applicable studies of good quality.
