Bacterial Vaginosis: Symptoms, Types, Causes and Treatment

Bacterial vaginosis (BV) is one of the most common vaginal conditions affecting women of reproductive age. Despite its frequency, BV remains a misunderstood and often misdiagnosed disorder, largely due to its complex origins, highly variable symptoms, and stubborn recurrence rates. In this article, we’ll break down the key symptoms, types, causes, and latest evidence on effective (and less effective) treatments for BV, drawing on up-to-date scientific research.

Symptoms of Bacterial Vaginosis

Bacterial vaginosis can be confusing to identify, both for patients and clinicians. Some women have unmistakable symptoms, while others are entirely asymptomatic. Understanding the spectrum of BV’s manifestations is essential for timely diagnosis and management.

Symptom	Description	Prevalence/Variability	Source(s)
Discharge	Homogeneous, gray, or yellowish	50-65% of symptomatic women	1 3 4
Odor	"Fishy" or amine-like, especially after intercourse	Reported by 25-35%	1 3 4
Irritation	Itching, burning or discomfort	Less common, <15%	2 4 5
Asymptomatic	No noticeable symptoms	Up to 50% of cases	2 3 4

Table 1: Key Symptoms

BV’s Symptom Spectrum

BV is notorious for its variability. About half of women with BV report no symptoms at all, making regular gynecological check-ups important for early detection 2 3 4. When symptoms do occur, they most commonly include:

• Abnormal vaginal discharge: This is usually described as thin, homogenous, and grayish-white or sometimes yellow. The discharge is often more noticeable after sexual intercourse 1 3.
• Odor: A strong, "fishy" or amine-like smell is characteristic, often intensifying after sex or during menstruation 1 3. However, studies show only a minority of women—about one in three—actually notice this odor 2 4.
• Irritation and discomfort: Unlike yeast infections or trichomoniasis, BV rarely causes significant itching, burning, or pain. When present, these symptoms are generally mild 2 4 5.
• Absence of symptoms: A substantial proportion, as many as 50%, may have BV without any noticeable symptoms 2 3 4. This asymptomatic presentation is clinically important, as BV still poses health risks even when silent.

Why Symptoms Matter

Recognizing the hallmark features of BV is crucial not only for symptom relief but also to prevent complications. BV increases the risk of pelvic inflammatory disease, adverse pregnancy outcomes, and the acquisition of sexually transmitted infections (STIs) 1 4 5. Even women without obvious symptoms can face these dangers, underscoring the value of vigilance and routine screening.

Types of Bacterial Vaginosis

While BV is often described as a single condition, recent research suggests there are different “types” or subgroups, primarily based on the microbial communities involved and the underlying pathophysiology.

Type/Subgroup	Key Microbial Features	Clinical Significance	Source(s)
Classic BV	Loss of lactobacilli, biofilm of G. vaginalis	Most common, typical symptoms	8 9 11
Biofilm-Associated	Dense, polymicrobial biofilm (Gardnerella spp.)	Higher recurrence, treatment resistance	8 15
Non-Biofilm Vaginosis	Dysbiosis without classic biofilm	Less well-characterized	8
Asymptomatic BV	Minimal symptoms, similar microbial shifts	Often undetected, still at risk	4 9

Table 2: BV Types

The Classic and Beyond

Classic BV

Traditionally, BV is characterized by a distinct shift in the vaginal microbiota: healthy, hydrogen-peroxide-producing lactobacilli are replaced by a diverse array of anaerobic bacteria, most notably Gardnerella vaginalis, Atopobium vaginae, Prevotella, Mobiluncus, and others 3 9 13. This shift leads to the clinical signs and symptoms most commonly associated with BV.

Biofilm-Associated BV

More recent discoveries have highlighted the role of biofilms—dense, multi-species bacterial communities embedded in a protective matrix—mainly composed of Gardnerella species 8 15. These biofilms confer resistance to both the body’s immune defenses and antibiotic treatments, which helps explain why BV so often recurs after standard therapy 8 15.

Non-Biofilm and Atypical BV

There are dysbiotic states that don’t fit the classic profile or lack a prominent biofilm. These are less well understood, but emerging molecular diagnostics are beginning to reveal additional patterns of microbial imbalance 8.

Asymptomatic BV

A significant number of women have the microbial features of BV without classic symptoms 4 9. Despite the absence of discomfort, these women remain at higher risk for reproductive complications, so the condition should not be dismissed as benign.

Why Types Matter

Understanding the different forms of BV is more than an academic exercise—these distinctions are driving the development of new diagnostic methods and treatment strategies, especially those targeting stubborn biofilms and recurrent disease 8 15.

Causes of Bacterial Vaginosis

The causes of BV are complex and multifactorial. Despite decades of research, no single cause has been definitively identified, but several contributing factors and mechanistic theories have emerged.

Cause/Factor	Description	Evidence/Notes	Source(s)
Microbiota Imbalance	Loss of lactobacilli, rise of anaerobes	Hallmark event	3 9 13
Sexual Activity	New/multiple partners, unprotected sex	Strongly associated	6 10 11
Biofilm Formation	Bacterial communities resist clearance	Linked to recurrence	8 15
Douching/Products	Disrupts vaginal environment	Increases risk	6
Host Immune Factors	Individual immune responses	Explains variability	9 10 12
Unclear Etiology	No single pathogen identified	Polymicrobial, multifactorial	10 12 13

Table 3: Causes and Risk Factors

The Microbial Shift

The root event in BV is a dramatic alteration in vaginal flora: the beneficial lactobacilli (especially those producing hydrogen peroxide) are depleted, making way for a proliferation of anaerobic bacteria like Gardnerella vaginalis, Atopobium vaginae, Prevotella, Mobiluncus, and others 3 9 13. This change disrupts the natural acidity (pH) of the vagina, creating an environment where pathogenic bacteria thrive.

The Role of Sexual Activity

Sexual behaviors influence the risk of developing BV. Having new or multiple sexual partners, unprotected intercourse, and even certain contraceptive practices are linked to higher rates of BV 6 10 11. However, BV is not strictly an STI, as it can also occur in sexually inactive women.

Biofilms and Persistence

Polymicrobial biofilms—especially those dominated by Gardnerella—play a central role in BV’s persistence and resistance to treatment. These structures protect bacteria from antibiotics and immune attack, leading to frequent recurrences 8 15.

Other Contributing Factors

• Douching and intravaginal products: These can disrupt the vaginal ecosystem, increasing BV risk 6.
• Host immune response: Individual variations in immune function may explain why some women develop recurrent or persistent BV while others do not, even with similar exposures 9 10 12.
• No single culprit: Despite efforts, no one organism or cause is consistently found in all cases of BV. It is now seen as a “syndrome” with multiple contributing factors 10 12 13.

Treatment of Bacterial Vaginosis

Managing BV remains a clinical challenge, largely due to high recurrence rates and the complex interplay of microbial communities. Both conventional and emerging therapies are employed, with varying degrees of success.

Treatment	Effectiveness/Notes	Limitations/Recurrence	Source(s)
Metronidazole (oral/topical)	Standard, high initial cure rates	Recurrence >50%	4 7 14 15
Clindamycin (oral/topical)	Alternative, similar to metronidazole	Recurrence common	4 14 15
Probiotics	May restore lactobacilli, adjunctive benefit	Evidence mixed, safe	16 17 18
Combination Therapy	Antibiotic + probiotic, or biofilm disruptor	Promising, under study	14 15
Partner Treatment	Limited data, may help in some cases	Not widely adopted	14

Table 4: Treatment Approaches

Conventional Antibiotics

Metronidazole and Clindamycin

The mainstay of BV treatment is antibiotics—specifically, metronidazole or clindamycin, given either orally or as a vaginal gel/cream 4 14 15. These drugs are initially effective for most women, but recurrence rates are high, with studies citing relapse in 50-80% of cases within three months 4 7 14 15. Neither drug reliably eradicates the protective biofilms formed by Gardnerella and other bacteria, which is believed to contribute to frequent relapses 7 8 15.

Probiotics

Probiotics, especially those containing strains of Lactobacillus, are being investigated as a way to restore the healthy vaginal microbiota following antibiotics 16 17 18. Meta-analyses and clinical trials suggest that probiotics may:

• Improve cure rates when used alongside antibiotics 18
• Offer a safe adjunctive or alternative option 16 17
• Have varying effectiveness depending on specific strains and populations studied 16 18

However, the evidence is not yet strong enough for universal recommendations, and further research is needed 17 18.

Combination and Novel Therapies

Recognizing the role of biofilms in persistent BV, researchers are exploring combination therapies—using traditional antibiotics together with agents that disrupt biofilms or targeted probiotics 14 15. Early data are promising but not yet definitive.

The Challenge of Recurrence

A major frustration with BV management is its relentless recurrence. Factors contributing to relapse include:

• Incomplete biofilm eradication 8 15
• Reinfection from sexual partners 14
• Host factors that predispose to microbiota imbalance 7 9

Addressing recurrence may ultimately require a multipronged approach: better diagnostics, novel antimicrobials, probiotics, and possibly even partner treatment regimens 14 15.

Conclusion

Bacterial vaginosis is a common but complex vaginal disorder that carries significant health risks, even when asymptomatic. Its diagnosis, classification, treatment, and prevention remain challenging due to its multifactorial causes and stubborn recurrence. However, emerging research into biofilms, the vaginal microbiome, and innovative therapies offers hope for improved management in the future.

Key Takeaways:

• BV often presents with abnormal discharge and odor, but up to half of women are asymptomatic 2 3 4.
• The condition involves a shift from lactobacilli dominance to a polymicrobial, often biofilm-associated, bacterial community 3 8 9 13.
• Risk factors include sexual activity, douching, and individual immune responses, but the exact cause is multifactorial 6 9 10 11 12.
• Standard antibiotic treatments are initially effective but plagued by high recurrence rates, likely due to biofilms 4 7 8 14 15.
• Probiotics and combination therapies show promise, but stronger evidence and innovative approaches are needed for long-term success 16 17 18.
• Even asymptomatic BV warrants attention due to associated risks with reproductive and sexual health 1 3 4.

Staying informed, recognizing symptoms (or their absence), and seeking timely care are crucial steps in managing BV and safeguarding reproductive health.