What are the causes of Bacterial Vaginosis (BV)?

From the Guidelines

Bacterial vaginosis (BV) is primarily caused by an imbalance in the vaginal microbiome, where beneficial lactobacilli bacteria decrease and harmful bacteria overgrow, as a result of various factors including douching, multiple sex partners, and lack of vaginal lactobacilli 1. This disruption can be triggered by several factors, including:

• Douching, which washes away good bacteria
• Multiple or new sexual partners, though BV isn't classified as a sexually transmitted infection
• Intrauterine devices (IUDs)
• Antibiotics that kill beneficial bacteria along with harmful ones Other contributing factors include hormonal changes during menstruation or pregnancy, smoking, and using scented feminine hygiene products. The cause of the microbial alteration is not fully understood, but it is associated with having multiple sex partners, douching, and lack of vaginal lactobacilli 1. BV is the most prevalent cause of vaginal discharge or malodor; however, up to 50% of women with BV may not report symptoms of BV 1. Women who have never been sexually active are rarely affected, and treatment of the male sex partner has not been beneficial in preventing the recurrence of BV 1. BV during pregnancy is associated with adverse pregnancy outcomes, including premature rupture of the membranes, preterm labor, preterm birth, and postpartum endometritis 1. The established benefit of therapy for BV in pregnant women is to relieve vaginal symptoms and signs of infection, and additional potential benefits of therapy include reducing the risk for infectious complications associated with BV during pregnancy and reducing the risk for other infections 1.

From the Research

Causes of Bacterial Vaginosis (BV)

• BV is associated with a state of vaginal dysbiosis, typically involving depletion of dominant populations of Lactobacillus 2
• The causes of this microbial succession are not known, but there may be multiple causes 2
• BV is characterized by the imbalanced vaginal flora, which changes the acidic environment normally dominated by Lactobacillus, and causes an overgrowth of anaerobic and facultative anaerobic bacteria such as Gardnerella vaginalis and Atopobium vaginae 3
• Vaginal dysbiosis-induced by an overgrowth of anaerobic bacteria is referred to as bacterial vaginosis (BV) 4

Risk Factors

• BV can increase the risk of contracting many sexually transmitted infections (STIs) such as human immunodeficiency virus (HIV), Neisseria gonorrhea (NG), Chlamydia trachomatis (CT), Trichomonas vaginalis (TV) and herpes simplex virus-2 (HSV-2) 5
• BV is closely related to adverse reproductive outcomes, which may be due to the infection of the vaginal flora ascending to the upper genital tract 3
• The incidence of BV is relatively high in infertile women 3

Microbiome

• The vaginal microbiome plays an important role in women's health and diseases 3
• For most women, the normal vaginal microbiota is dominated by Lactobacillus, which can maintain a healthy vaginal environment by producing lactic acid, H2O2 and bacteriocin, etc. 3
• Gardnerella spp. is the most abundant organism in women with asymptomatic BV 4
• After treatment with metronidazole, there is an observed decline of Lactobacillus and Prevotella species 4