2.5.6 Bacterial Vaginosis

Grading & Level of Importance: B

Review:

2026

W. Burgdorf, Munich; R. Woolf, J. McGrath, London;
Revised by E. Hiltunen-Back, Helsinki; M. Janier, Paris; A. Ranki, Helsinki; A. Salava, Helsinki

Overview:

ICD-11
Synonyms
Epidemiology
Definition
Aetiology & Pathogenesis
Signs & Symptoms
Localisation
Classification
Laboratory & other workups
Dermatopathology
Course
Complications
Diagnosis
Differential Diagnosis
Prevention & Therapy
Special

ICD-11

MF3A

Synonyms

Nonspecific vaginitis, Gardnerella vaginitis, Bacterial vaginitis.

Epidemiology

A very common cause of vaginal symptoms in women of reproductive age; lifelong prevalence in Europe 15-20 %.

Definition

A disturbance of the normal bacterial flora of the vulva and/or vagina causing a malodorous discharge.

Bacterial vaginosis is a common cause of vulvovaginal symptoms in women of the reproductive age with the main symptom of malodorous vaginal discharge. It is not contagious and not a sexually transmitted infection, but can start after frequent sexual intercourse or intercourse with a new partner.

Aetiology & Pathogenesis

Pathogenesis not completely understood; disturbances of normal vaginal microbiota (Lactobacillus spp.) suspected. Detectable overgrowth of anaerobic bacteria with an elevation of the vaginal pH. Predisposing factors: recent use of broad-spectrum antibiotics, use of an intrauterine device, high number of sexual partners.

The pathogenesis of bacterial vaginosis is not completely understood, but disturbances of normal vaginal microbes (Lactobacillus spp. are normally the most abundant) are suspected. There is a detectable overgrowth of anaerobic bacteria (e.g. Gardnerella and Bacteroides species) with an elevation of the vaginal pH. Predisposing factors for bacterial vaginosis are a recent use of broad-spectrum antibiotics, use of an intrauterine device and a high number of sexual partners.

Signs & Symptoms

Main symptom is a malodorous, milky or grey-white homogeneous vaginal discharge. The discharge can cause irritation of the vulvar skin. The odour of the discharge has a fishy smell and is a common complaint.

Localisation

Usually localized to vulvar skin and vaginal mucosa.

Classification

Not applicable.

Laboratory & other workups

Microscopy of a vaginal smear shows epithelial cells with many adherent cocci (clue-cells) with almost no leucocytes. Vaginal pH strip test (pH > 4.5). If drops of potassium hydroxide solution are applied on the speculum, a fishy smell can be provoked (KOH-test). Some patients with positive test results do not have symptoms. Findings of bacterial vaginosis can be normal in asymptomatic postmenopausal women.

Typical microscopy of a vaginal smear shows epithelial cells with many adherent cocci (clue-cells) with almost no leucocytes. The vaginal pH strip test shows an elevated pH (> 4.5), unlike in vulvovaginal candidiasis. If some drops of potassium hydroxide solution are applied on the speculum, a fishy smell can be provoked (KOH-test). The exclusion of other vaginitis causes may be necessary (e.g. fungal and bacterial culture, trichomonas). Tests to exclude concomitant STI-infections may be offered.

Some patients with positive test results (e.g. microscopy of the vaginal smear) do not have symptoms. Findings of bacterial vaginosis can be normal in asymptomatic postmenopausal women.

Dermatopathology

Not necessary.

Course

Symptoms usually wax and wane; may last some days to weeks.

Complications

During pregnancy, there have been reports associating bacterial vaginosis with premature labour and perinatal infections (chorioamnionitis).

Diagnosis

Based on typical clinical features and complementary tests suggestive for bacterial vaginosis.

Differential Diagnosis

Vaginal discharge caused by other causes of vulvovaginitis (candida, aerobic and trichomonas vaginitis). If there is discharge from the cervix, genital chlamydia and gonorrhoea should be excluded; in recurrent cases and elderly women, a colposcopy to exclude malignancies.

Prevention & Therapy

Usually not preventable. Recurrences after treatment are common due to the biofilm produced by G. vaginalis. Oral combined contraceptives can reduce recurrence.

Has a tendency to spontaneously subside and treatments are not always necessary. Should be treated during pregnancy because of possible association with perinatal complications.

Effective treatments are a single dose of p.o. metronidazole 2 g or a course of p.o. metronidazole 400-500 mg t.i.d. for 5-7 days.

Bacterial vaginosis is usually not preventable. Recurrences after treatment are common due to the biofilm produced by G. vaginalis. Oral combined contraceptives can reduce recurrence.

The symptoms have a tendency to spontaneously subside and treatments are not always necessary. During pregnancy, bacterial vaginosis should be treated because of the possible association with perinatal complications.

Effective treatments are a single dose of p.o. metronidazole 2 g or a course of p.o. metronidazole 400-500 mg t.i.d. for 5-7 days. Local therapy with intravaginal clindamycin is an alternative, especially in pregnancy. Vaginal tablets that reduce the pH to encourage restoration of normal vaginal lactobacilli may also be tried.

Special