Bacterial vaginosis

Overview

Bacterial vaginosis (BV) is a common condition in women characterised by an imbalance of microorganisms in the vagina. In cases of BV, there is a decrease in the number of normal hydrogen peroxide-producing Lactobacillus species and an excessive growth of anaerobic bacteria, such as:

• Gardnerella spp.

• Prevotella spp.

• Mobilincus spp.

• Ureaplasma urealyticum

• Mycoplasma hominis

These could lead to an increase in pH from less than 4.5 to as high as 7.0.

BV is not considered a sexually transmitted infection (STI), but it occurs more commonly in sexually active women. The exact role of sexual transmission in the pathogenesis of BV vaginal dysbiosis is unclear.

Disease epidemiology

BV is the most common vaginal infection found in women of reproductive age and is estimated to occur in anywhere from 5% to 70% of women. Globally, it is more commonly reported in low-resource settings and areas with limited access to healthcare.

Pathogen(s)

The organisms typically associated with BV are:

• G. vaginalis

• Bacteroides spp

• Prevotella spp

• Mobiluncus spp

• Ureaplasma urealyticum

• Mycoplasma hominis

Transmission

BV is not considered a sexually transmitted infection, but it occurs more commonly in sexually active women. The exact role of sexual transmission in the pathogenesis of BV vaginal dysbiosis is unclear.

Incubation period: 4 days

Infectious period: NA

Clinical features

BV may be asymptomatic. However, common symptoms include:

• Unusual vaginal discharge that is thin and grayish-white

• A fishy odour from the vagina, especially after sex

• Itching or irritation around the vagina

• Burning sensation during urination

At times, BV will go away without treatment. However, if untreated it can lead to:

• Problems in pregnancy (for example, spontaneous abortion and preterm delivery for pregnant women with BV)

• Higher risk of STIs and HIV

• Pelvic inflammatory disease

Risk factors

Risk factors include:

• Vaginal douching

• Receptive cunnilingus

• Recent change of sex partner

• Smoking

• Presence of an STI

Diagnosis

BV is often diagnosed by the Amsel criteria, with at least three of the four criteria present:

• Thin homogenous vaginal discharge that coats the vaginal wall and vestibule

• pH of vaginal fluid more than 4.5

• Positive amine (fish-like) odour test (“whiff test”) before or after addition of 10% KOH

• Presence of clue cells on microscopy of vaginal discharge

Treatment and management

Patients should avoid vaginal douching, use of shower gels, antiseptic agents, or shampoos in the bath.

Recommended regimens for BV:

• Metronidazole 400mg to 500mg orally 2 times a day, for 5 to 7 days

• Metronidazole 2g orally single dose;

• Metronidazole gel 0.75% one full applicator (5g) intravaginally daily for 5 days

• Clindamycin cream 2% one full applicator (5g) intravaginally at bedtime for 7 days

Recommended regimens for BV in pregnancy:

• Metronidazole 400mg to 500mg orally 2 times a day, for 7 days

• Metronidazole 200mg orally 3 times a day, for 7 days

• Clindamycin 300mg orally 2 times a day, for 7 days

Follow-up is not necessary if symptoms resolve. For high-risk pregnant women, a one-month follow-up visit is recommended to evaluate if treatment is successful. Long-term maintenance regimens are not recommended.

Alternative regimen can be given if the disease recurs. Refer to DSC’s website for more information on alternative regimens.

Precaution, prevention, and control

The cause of BV is not yet understood. The following basic preventive measures may help lower the risk of getting BV:

• Avoid douching and feminine sprays

• Not having sex

• Limit the number of sex partners

• Use condoms consistently

Notification

BV is not a notifiable condition. Please refer to the Infectious Disease Notification for more information.

Resources

Refer to the Department of Sexually Transmitted Infections Control's website for more information on alternative regimens.