What is bacterial vaginosis

Bacterial vaginosis is a common infection of the vagina when there is too much of certain bacteria in the vagina, with a loss of protective lactic-acid producing Lactobacillus species in conjunction with increases in the concentration of facultative and strict anaerobic bacteria including Gardnerella vaginalis, Prevotella spp., Atopobium vaginae, Sneathia spp., and other bacterial vaginosis-associated bacteria ¹. Bacterial vaginosis can increase your risk of acquiring a number of sexually transmitted infections (STIs), including HIV ². In addition, bacterial vaginosis may contribute to adverse birth outcomes, such as premature birth, low birth weight, and premature rupture of membranes ³. Bacterial vaginosis is the most common cause of vaginal discharge and vaginal infection in women ages 15-44, but any woman can get bacterial vaginosis ⁴. The estimated prevalence of bacterial vaginosis among reproductive-aged women in the United States has ranged from a low of 17% to a high of 47%, with an overall estimated prevalence of approximately 25 to 30% ⁴, ⁵. In these studies, many of the women with bacterial vaginosis were asymptomatic. Data on the incidence of bacterial vaginosis are extremely limited.

Although the actual cause of bacterial vaginosis is currently unknown, scientists believed bacterial vaginosis is linked to an imbalance of “good” and “harmful” bacteria that are normally found in a woman’s vagina, which could be caused by certain activities that increase your risk, such as unprotected sex or frequent douching. Increased bacterial vaginosis prevalence is associated with a greater number of male sex partners, sex with a female partner, douching and herpes simplex virus type 2 (HSV-2) infection ⁶, ⁷. A reduced risk is associated with condom use, male partners who are circumcised, and oral contraceptive pills ⁸, ⁹. Increasing evidence suggests that sexual activity is integral to the development of incident bacterial vaginosis in most persons, as it correlates with the frequency of sexual activity, younger age at sexual debut, participating in anal and oral sex, and use of vaginal sex toys ¹⁰, ⁵. The role of sexual activity in bacterial vaginosis is also supported by indirect evidence, including (1) the absence of bacterial vaginosis in women prior to sexual debut, (2) concordant vaginal flora among women in same-sex partnerships, and (3) elevated rates of bacterial vaginosis-associated bacterial colonization (as measured with penile swabs) among men engaging in extramarital sexual relationships, as compared with men who are monogamous ¹¹, ¹².

Bacterial vaginosis is harmless and easily treated. Bacterial vaginosis is not classed as a sexually transmitted infection (STI) or sexually transmitted disease (STD). However, having bacterial vaginosis can increase your chance of getting a STD (e.g., HIV, N. gonorrhoeae, C. trachomatis, and HSV- 2) including developing pelvic inflammatory disease (PID). Bacterial vaginosis also increases the risk for HIV transmission to male sex partners ¹³. Although bacterial vaginosis-associated bacteria can be found in the male genitalia, treatment of male sex partners has not been beneficial in preventing the recurrence of bacterial vaginosis ¹⁴.

Please note, bacterial vaginosis must not be confused with vaginitis (inflammation of the vagina). Vaginitis is defined as any condition with symptoms of abnormal vaginal discharge, odor, irritation, itching, or burning ¹⁵. The most common causes of vaginitis are bacterial vaginosis, vulvovaginal candidiasis, and trichomoniasis ¹⁵. Bacterial vaginosis is implicated in 40% to 50% of vaginitis cases when a cause is identified, with vulvovaginal candidiasis accounting for 20% to 25% and trichomoniasis for 15% to 20% of cases. Noninfectious causes, including atrophic, irritant, allergic, and inflammatory vaginitis, are less common and account for 5% to 10% of vaginitis cases. Most women have at least one episode of vaginitis during their lives, making it the most common gynecologic diagnosis in primary care ¹⁵.

Bacterial vaginosis key facts

• The vagina is a dynamic ecosystem that changes with age (see Figure 1). Under normal conditions, 70-90% of the vaginal bacterial species in healthy premenopausal women are Lactobacilli ¹⁶. Among more than 200 Lactobacillus species, over 20 species have been found in the vaginal flora ¹⁷. Sequencing of the 16 rRNA gene revealed that the vaginal bacterial community, mainly composed of Lactobacilli, is classified into five groups named community state types (CST), namely I, II, III, IV and V ¹⁸. Four of these groups are dominated by Lactobacillus. The first is dominated by Lactobacillus crispatus, the second by Lactobacillus gasseri, the third by Lactobacillus iners, and the fifth by Lactobacillus jensenii, while the fourth contains a smaller proportion of Lactobacilli but is composed of a polymicrobial mixture of strict and facultative anaerobes (Gardnerella, Atopobium, Mobiluncus, Prevotella…) ¹⁹.
• Normal vaginal discharge is clear to white, odorless, and of high viscosity. The normal bacterial microbiota is dominated by Lactobacillus spp. (i.e. Lactobacillus crispatus), but a variety of other facultative and strict anaerobic bacteria are also present at much lower levels. Lactobacillus species are a major part of the lactic acid bacteria group (i.e. they convert sugars to lactic acid) in your vagina, which helps to maintain a normal acidic vaginal pH of 3.8 to 4.5. Some lactobacilli produce H₂O₂ (hydrogen peroxide), which serves as a host defense mechanism and kills bacteria and viruses. Lactobacillus is a genus of Gram-positive, facultative anaerobic or microaerophilic, rod-shaped, non-spore-forming bacteria. Usually, “good” bacteria (lactobacilli) outnumber “bad” bacteria (anaerobes). But if there are too many anaerobic bacteria, they upset the natural balance of microorganisms in your vagina and cause bacterial vaginosis.
• Bacterial vaginosis is the most common vaginal condition in women ages 15 to 44 ²⁰. But women of any age can get it, even if they have never had sex.
  • Researchers are still studying how women get bacterial vaginosis. You can get bacterial vaginosis without having sex, but bacterial vaginosis is more common in women who are sexually active. Having a new sex partner or multiple sex partners, as well as douching, can upset the balance of good and harmful bacteria in your vagina ²⁰. This raises your risk of getting bacterial vaginosis.
• The Centers for Disease Control and Prevention (CDC) recommends all women with bacterial vaginosis should be tested for HIV and other sexually transmitted diseases (STDs) ²¹.
• Bacterial vaginosis is the most common cause of vaginal symptoms among women, but it is not clear what role sexual activity plays in the development of bacterial vaginosis.
• You may be more at risk for bacterial vaginosis if you:
  • Have a new sex partner
  • Have multiple sex partners
  • Douche ²²
  • Do not use condoms or dental dams
  • Are pregnant. bacterial vaginosis is common during pregnancy. About 1 in 4 pregnant women get bacterial vaginosis ²³. The risk for bacterial vaginosis is higher for pregnant women because of the hormonal changes that happen during pregnancy.
  • Are African-American. bacterial vaginosis is twice as common in African-American women as in white women ²⁴
  • Have an intrauterine device (IUD), especially if you also have irregular bleeding ²⁵
• Bacterial vaginosis in pregnancy has been linked to several obstetric complications, including late miscarriage, premature rupture of membranes, premature delivery, and low birth weight at delivery ³, ²⁶, ²⁷, ²⁸. Bacterial vaginosis has also been associated with gynecologic complications, particularly an increased risk of post-operation infections after gynecological procedures ²⁹. There are some data to suggest bacterial vaginosis may cause additional gynecologic complications, including endometritis, pelvic inflammatory disease (PID) and infertility, but prospective, longitudinal studies are needed to conclusively determine if bacterial vaginosis clearly causes these complications ³⁰.

The prevalence in the United States is estimated to be 21.2 million (29.2%) among women ages 14–49, based on a nationally representative sample of women who participated in NHANES 2001–2004. The following are other findings from this study ³¹.

• Most women found to have bacterial vaginosis (84%) reported no symptoms.
• Women who have not had vaginal, oral, or anal sex can still be affected by bacterial vaginosis (18.8%), as can pregnant women (25%), and women who have ever been pregnant (31.7%).
• Prevalence of bacterial vaginosis increases based on lifetime number of sexual partners.
• Non white women have higher rates (African-American 51%, Mexican Americans 32%) than white women (23%).

Bacterial vaginosis is traditionally diagnosed with Amsel criteria, although Gram stain is the diagnostic standard ¹⁵.

Bacterial vaginosis is treated with oral metronidazole, intravaginal metronidazole, or intravaginal clindamycin ¹⁵. Treatment is especially important for pregnant women. Pregnant women with bacterial vaginosis may deliver premature (early) or low birth-weight babies.

Recommended antibiotics for bacterial vaginosis ²¹:

• Metronidazole 500 mg orally twice a day for 7 days
• OR Metronidazole gel 0.75%, one full applicator (5 g) intravaginally, once a day for 5 days
• OR Clindamycin cream 2%, one full applicator (5 g) intravaginally at bedtime for 7 days

Alcohol consumption should be avoided during treatment with nitroimidazoles. To reduce the possibility of a disulfiram-like reaction, abstinence from alcohol use should continue for 24 hours after completion of metronidazole. Clindamycin cream is oil-based and might weaken latex condoms and diaphragms for 5 days after use (refer to clindamycin product information for additional information).

Women should be advised to refrain from sexual activity or use condoms consistently and correctly during the treatment regimen. Douching might increase the risk for relapse, and no data support the use of douching for treatment or relief of symptoms.

You can buy treatments for bacterial vaginosis over the counter, but there’s no clear proof they work.

Figure 1. Vaginal microbiome over a woman’s lifespan

[Source ³² ]

Figure 2. Bacterial vaginosis versus healthy vaginal flora  

[Source ³² ]

Figure 3. Bacterial vaginosis clue cells (vaginal cells covered with bacteria that are a sign of bacterial vaginosis)

[Source ³³ ]

Home remedies for bacterial vaginosis

To help relieve symptoms and prevent bacterial vaginosis from returning:

DO

• use water and an emollient, such as E45 cream, or plain soap to wash your genital area
• have showers instead of baths
• stay out of hot tubs or whirlpool baths.
• wash your vagina and anus with a gentle, non-deodorant soap.
• rinse completely and gently dry your genitals well.
• use unscented tampons or pads.
• wear loose-fitting clothing and cotton underwear. Avoid wearing pantyhose.
• wipe from front to back after you use the bathroom.

DON’T

• use perfumed soaps, bubble bath or shower gel
• use vaginal deodorants, washes or douches
• put antiseptic liquids in the bath
• use strong detergents to wash your underwear
• smoke

How do you get bacterial vaginosis?

Researchers do not know the cause of bacterial vaginosis or how some women get it. Scientists do know that the infection typically occurs in sexually active women. Bacterial vaginosis is linked to an imbalance of “good” and “harmful” bacteria that are normally found in a woman’s vagina. Having a new sex partner or multiple sex partners, as well as douching, can upset the balance of bacteria in the vagina. This places a woman at increased risk for getting bacterial vaginosis.

Researchers also do not know how sex contributes to bacterial vaginosis. There is no research to show that treating a sex partner affects whether or not a woman gets bacterial vaginosis. Having bacterial vaginosis can increase your chances of getting other sexually transmitted infections (STIs).

Bacterial vaginosis rarely affects women who have never had sex.

You cannot get bacterial vaginosis from toilet seats, bedding, or swimming pools.

How can I avoid getting bacterial vaginosis?

Doctors and scientists do not completely understand how bacterial vaginosis spreads. There are no known best ways to prevent it.

The following basic prevention steps may help lower your risk of developing bacterial vaginosis:

• Not having sex;
• Limiting your number of sex partners;
• Always using a condom when you have sex; and
• Not douching. Douching removes the healthy bacteria in your vagina that protect against infection.

How do I know if I have bacterial vaginosis?

Many women with bacterial vaginosis do not have symptoms. If you do have symptoms, you may notice:

• A thin white or gray vaginal discharge;
• Pain, itching, or burning in the vagina;
• A strong fish-like odor, especially after sex;
• Burning when urinating;
• Itching around the outside of the vagina.

How will my doctor know if I have bacterial vaginosis?

A health care provider will examine your vagina for signs of vaginal discharge. Your provider can also perform laboratory tests on a sample of vaginal fluid to determine if bacterial vaginosis is present. Bacterial vaginosis is traditionally diagnosed with Amsel criteria, although Gram stain is the diagnostic standard ¹⁵.

What happens if I don’t get treated?

Bacterial vaginosis can cause some serious health risks, including ²¹:

• Increasing your chance of getting HIV if you have sex with someone who is infected with HIV;
• If you are HIV positive, increasing your chance of passing HIV to your sex partner;
• Making it more likely that you will deliver your baby too early if you have bacterial vaginosis while pregnant. Bacterial vaginosis can lead to premature birth or a low-birth-weight baby (smaller than 5 1/2 pounds at birth). All pregnant women with symptoms of bacterial vaginosis should be tested and treated if they have it;
• Increasing your chance of getting other STDs, such as chlamydia and gonorrhea. These bacteria can sometimes cause pelvic inflammatory disease (PID), which can make it difficult or impossible for you to have children.

Recurring bacterial vaginosis

It’s common for bacterial vaginosis to come back, usually within 3 months.

You’ll need to take treatment for longer (up to 6 months) if you keep getting bacterial vaginosis (you get it more than twice in 6 months). Your doctor or sexual health clinic will recommend how long you need to treat it.

They can also help identify if something is triggering your bacterial vaginosis, such as sex or your period.

Can bacterial vaginosis be cured?

Bacterial vaginosis will sometimes go away without treatment. But if you have symptoms of bacterial vaginosis you should be checked and treated. It is important that you take all of the medicine prescribed to you, even if your symptoms go away. Your doctor can treat bacterial vaginosis with antibiotics, but bacterial vaginosis may recur even after treatment. Treatment may also reduce the risk for some STDs (sexually transmitted diseases).

Male sex partners of women diagnosed with bacterial vaginosis generally do not need to be treated. bacterial vaginosis may be transferred between female sex partners ³⁵.

How can I lower my risk of bacterial vaginosis?

Researchers do not know exactly how bacterial vaginosis spreads. Steps that might lower your risk of bacterial vaginosis include:

• Keeping your vaginal bacteria balanced. Use warm water only to clean the outside of your vagina. You do not need to use soap. Even mild soap can cause irritate your vagina. Always wipe front to back from your vagina to your anus. Keep the area cool by wearing cotton or cotton-lined underpants.
• Not douching. Douching upsets the balance of good and harmful bacteria in your vagina. This may raise your risk of bacterial vaginosis. It may also make it easier to get bacterial vaginosis again after treatment. Doctors do not recommend douching.
• Not having sex. Researchers are still studying how women get bacterial vaginosis. You can get bacterial vaginosis without having sex, but bacterial vaginosis is more common in women who have sex.
• Limiting your number of sex partners. Researchers think that your risk of getting bacterial vaginosis goes up with the number of partners you have.

How can I protect myself if I am a female and my female partner has bacterial vaginosis?

If your partner has bacterial vaginosis, you might be able to lower your risk by using protection during sex.

• Use a dental dam every time you have sex. A dental dam is a thin piece of latex that is placed over the vagina before oral sex.
• Cover sex toys with condoms before use. Remove the condom and replace it with a new one before sharing the toy with your partner.

What is the difference between bacterial vaginosis and a vaginal yeast infection?

Bacterial vaginosis and vaginal yeast infections are both common causes of vaginal discharge. They have similar symptoms, so it can be hard to know if you have bacterial vaginosis or a yeast infection. Only your doctor or nurse can tell you for sure if you have bacterial vaginosis.

With bacterial vaginosis, your discharge may be white or gray but may also have a fishy smell. Discharge from a yeast infection may also be white or gray but may look like cottage cheese.

What should I do if I have bacterial vaginosis?

Bacterial vaginosis is easy to treat. If you think you have bacterial vaginosis:

• See a doctor. Antibiotics will treat bacterial vaginosis.
• Take all of your medicine. Even if symptoms go away, you need to finish all of the antibiotic.
• Tell your sex partner(s) if she is female so she can be treated.
• Avoid sexual contact until you finish your treatment.
• See your doctor again if you have symptoms that don’t go away within a few days after finishing the antibiotic.

Is it safe to treat pregnant women who have bacterial vaginosis?

Yes. The medicine used to treat bacterial vaginosis is safe for pregnant women. All pregnant women with symptoms of bacterial vaginosis should be tested and treated if they have it.

If you do have bacterial vaginosis, you can be treated safely at any stage of your pregnancy. You will get the same antibiotic given to women who are not pregnant.

Bacterial vaginosis in pregnancy

Pregnant women can get bacterial vaginosis. Pregnant women with bacterial vaginosis are more likely to have babies born premature (early) or with low birth weight than pregnant women without bacterial vaginosis. Low birth weight means having a baby that weighs less than 5.5 pounds at birth.

Treatment is especially important for pregnant women and is recommended for all symptomatic pregnant women. Studies have been undertaken to determine the efficacy of bacterial vaginosis treatment among pregnant women, including two trials demonstrating that metronidazole was efficacious during pregnancy using the 250-mg regimen ³⁶, ³⁷; however, metronidazole administered at 500 mg twice daily can be used. One trial involving a limited number of participants revealed treatment with oral metronidazole 500 mg twice daily to be equally effective as metronidazole gel, with cure rates of 70% using Amsel criteria to define cure ³⁸. Another trial demonstrated a cure rate of 85% using Gram-stain criteria after treatment with oral clindamycin ³⁹. Multiple studies and meta-analyses have failed to demonstrate an association between metronidazole use during pregnancy and teratogenic or mutagenic effects in newborns ⁴⁰, ⁴¹. Although older studies indicated a possible link between use of vaginal clindamycin during pregnancy and adverse outcomes for the newborn, newer data demonstrate that this treatment approach is safe for pregnant women ⁴². Because oral therapy has not been shown to be superior to topical therapy for treating symptomatic bacterial vaginosis in effecting cure or preventing adverse outcomes of pregnancy, symptomatic pregnant women can be treated with either of the oral or vaginal regimens recommended for nonpregnant women. Although adverse pregnancy outcomes, including premature rupture of membranes, preterm labor, preterm birth, intra-amniotic infection, and postpartum endometritis have been associated with symptomatic bacterial vaginosis in some observational studies, treatment of bacterial vaginosis in pregnant women can reduce the signs and symptoms of vaginal infection. A meta-analysis has concluded that no antibiotic regimen prevented preterm birth (early or late) in women with bacterial vaginosis (symptomatic or asymptomatic). However, in one study, oral bacterial vaginosis therapy reduced the risk for late miscarriage, and in two additional studies, such therapy decreased adverse outcomes in the neonate ⁴³.

Treatment of asymptomatic bacterial vaginosis among pregnant women who are at high risk for preterm delivery (i.e., those with a previous preterm birth) has been evaluated by several studies, which have yielded mixed results. Seven trials have evaluated treatment of pregnant women with asymptomatic bacterial vaginosis at high risk for preterm delivery: one showed harm ⁴⁴, two showed no benefit ⁴⁵, ⁴⁶, and four demonstrated benefit ³⁶, ³⁷, ⁴⁷, ⁴⁸.

Similarly, data are inconsistent regarding whether treatment of asymptomatic bacterial vaginosis among pregnant women who are at low risk for preterm delivery reduces adverse outcomes of pregnancy. One trial demonstrated a 40% reduction in spontaneous preterm birth among women using oral clindamycin during weeks 13–22 of gestation ⁴⁸. Several additional trials have shown that intravaginal clindamycin given at an average gestation of >20 weeks did not reduce likelihood of preterm birth ⁴⁶, ⁴⁹. Therefore, evidence is insufficient to recommend routine screening for bacterial vaginosis in asymptomatic pregnant women at high or low risk for preterm delivery for the prevention of preterm birth ⁵⁰.

Although metronidazole crosses the placenta, no evidence of teratogenicity or mutagenic effects in infants has been found in multiple cross-sectional and cohort studies of pregnant women ⁵¹. Data suggest that metronidazole therapy poses low risk in pregnancy ⁵².

Metronidazole is secreted in breast milk. With maternal oral therapy, breastfed infants receive metronidazole in doses that are less than those used to treat infections in infants, although the active metabolite adds to the total infant exposure. Plasma levels of the drug and metabolite are measurable, but remain less than maternal plasma levels ⁵³. Although several reported case series found no evidence of metronidazole-associated adverse effects in breastfed infants, some clinicians advise deferring breastfeeding for 12–24 hours following maternal treatment with a single 2-g dose of metronidazole ⁵⁴. Lower doses produce a lower concentration in breast milk and are considered compatible with breastfeeding ⁵⁵. Data from studies of human subjects are limited regarding the use of tinidazole in pregnancy; however, animal data suggest that such therapy poses moderate risk. Thus tinidazole should be avoided during pregnancy ⁵².

Bacterial vaginosis symptoms

Approximately 50 to 75% of women with bacterial vaginosis don’t have any signs or symptoms ⁵⁶. At other times, bacterial vaginosis may cause ⁵⁷, ⁵⁸:

• A white (milky) or gray vaginal discharge that coats the walls of the vagina. It may also be foamy or watery.
• Vaginal discharge with an unpleasant or fish-like odor (“fishy smell”), especially after sex and around the time of menstruation.
• Vaginal pain or itching inside and outside the vagina
• Burning during urination
• Vaginal irritation

These symptoms may be similar to vaginal yeast infections and other health problems. Only your doctor or nurse can tell you for sure whether you have bacterial vaginosis. Doctors are unsure of the incubation period for bacterial vaginosis.

Symptoms may remit spontaneously. Bacterial vaginosis does not typically cause itch (pruritus), burning, dysuria (discomfort, pain or burning when urinating), painful intercourse (dyspareunia), vaginal inflammation, or vulvar swelling ⁵⁸. Qualitative studies have shown that bacterial vaginosis can negatively impact self-esteem, sexual relationships, and quality of life ⁵.

Bacterial vaginosis complications

Bacterial vaginosis doesn’t generally cause complications. Sometimes, having bacterial vaginosis may lead to:

• Preterm birth. In pregnant women, bacterial vaginosis is linked to premature deliveries and low birth weight babies.
• Sexually transmitted infections (STIs). Having bacterial vaginosis makes women more susceptible to sexually transmitted infections, such as HIV, herpes simplex virus, chlamydia or gonorrhea. If you have HIV, bacterial vaginosis increases the odds that you’ll pass the virus on to your partner.
• Infection risk after gynecologic surgery. Having bacterial vaginosis may increase the risk of developing a post-surgical infection after procedures such as hysterectomy or dilation and curettage (D&C).
• Pelvic inflammatory disease (PID). Bacterial vaginosis can sometimes cause PID, an infection of the uterus and the fallopian tubes that can increase the risk of infertility.

Bacterial vaginosis causes

Bacterial vaginosis occurs when there’s a change in the natural balance of bacteria in your vagina. What causes this to happen isn’t fully known, but you’re more likely to get it if:

• you’re sexually active
• you’ve had a change of partner
• you have an IUD (contraception intrauterine device)
• you use perfumed products in or around your vagina

Bacterial vaginosis is not classed as an STI, even though it can be triggered by sex. A woman can pass it to another woman during sex.

But women who haven’t had sex can also get bacterial vaginosis.

Current understanding of the pathogenesis of bacterial vaginosis suggests loss of the normal hydrogen peroxide (H₂O₂) producing Lactobacillus species in the vagina by multiple facultative and strict anaerobic bacteria (e.g., Prevotella sp. and Mobiluncus sp.), Gardnerella Vaginalis, Ureaplasma, Mycoplasma, and numerous fastidious or uncultivated anaerobes, which leads to a subsequent vaginal dysbiosis and a proinflammatory state ¹. To date, however, the exact cause of bacterial vaginosis has not been determined, despite extensive research ⁵⁹. Some women experience transient vaginal microbial changes, whereas others experience them for longer intervals of time. Among women presenting for care, bacterial vaginosis is the most prevalent cause of vaginal discharge or malodor; however, in a nationally representative survey, most women with bacterial vaginosis were asymptomatic ⁶⁰.

Bacterial vaginosis is associated with having multiple male or female partners, a new sex partner, douching, lack of condom use, and lack of vaginal lactobacilli; women who have never been sexually active are rarely affected ⁶¹. The cause of the microbial alteration that precipitates bacterial vaginosis is not fully understood, and whether bacterial vaginosis results from acquisition of a single sexually transmitted pathogen is not known. Nonetheless, women with bacterial vaginosis are at increased risk for the acquisition of some STDs (e.g., HIV, N. gonorrhoeae, C. trachomatis, and HSV- 2), complications after gynecologic surgery, complications of pregnancy, and recurrence of bacterial vaginosis ⁶². Bacterial vaginosis also increases the risk for HIV transmission to male sex partners ¹³. Although bacterial vaginosis-associated bacteria can be found in the male genitalia, treatment of male sex partners has not been beneficial in preventing the recurrence of bacterial vaginosis ¹⁴.

The following summarizes current step-by-step conceptual models for the pathogenesis of bacterial vaginosis ¹, ², ⁶³:

• In the baseline state, in a healthy vaginal microbiome, Lactobacillus species are dominant, and they produce lactic acid from glycogen, a process that maintains a low vaginal pH; this acidic pH environment inhibits the growth of other bacterial species that are normally present in the vagina at very low levels.
• The process of vaginal dysbiosis usually begins with colonization of the vagina with a virulent strain of Gardnerella vaginalis, typically following a sexual exposure; the proliferation of this organism displaces vaginal lactobacilli and creates a biofilm scaffolding conducive to recruiting Prevotella bivia (and other bacterial vaginosis-associated bacteria).
• Gardnerella vaginalis and Prevotella bivia engage in a synergistic relationship in which proteolysis by Gardnerella vaginalis produces amino acids that enhance the growth of Prevotella bivia. In turn, ammonia produced by Prevotella bivia enhances the growth of Gardnerella vaginalis.
• Sialidase produced by both Prevotella bivia and Gardnerella vaginalis promotes breakdown of the mucin layer of the vaginal epithelium and increase adherence of other strict anaerobes, including Atopobium vaginae, Megasphaera type I, and others which join the bacterial vaginosis biofilm on the upper layers.
• Atopobium vaginae stimulates a strong host immune response from vaginal epithelial cells, leading to localized cytokine and beta-defensin production
• Gradually the healthy normal dominant vaginal lactobacilli are replaced by Gardnerella vaginalis, Atopobium vaginae, bacterial vaginosis-associated bacteria-2 (BVAB-2), and Megasphaera type I.
• In the final phase of this transition to bacterial vaginosis, mucus degradation occurs, the vaginal pH is elevated, multiple harmful compounds are produced (biogenic amines, toxic metabolites, and proinflammatory cytokines)—all resulting in a final state of vaginal dysbiosis and inflammation, which may progress to cause vaginal symptoms and adverse outcomes associated with this infection.

Risk factors for developing bacterial vaginosis

Risk factors for bacterial vaginosis include:

• Having multiple sex partners or a new sex partner. Doctors don’t fully understand the link between sexual activity and bacterial vaginosis, but the condition occurs more often in women who have multiple sex partners or a new sex partner. Bacterial vaginosis also occurs more frequently in women who have sex with women.
• Douching. The practice of rinsing out your vagina with water or a cleansing agent (douching) upsets the natural balance of your vagina. This can lead to an overgrowth of anaerobic bacteria, and cause bacterial vaginosis. Since the vagina is self-cleaning, douching isn’t necessary.
• Natural lack of lactobacilli bacteria. If your natural vaginal environment doesn’t produce enough of the good lactobacilli bacteria, you’re more likely to develop bacterial vaginosis.

Bacterial vaginosis prevention

To help prevent bacterial vaginosis:

• Minimize vaginal irritation. Use mild, nondeodorant soaps and unscented tampons or pads.
• Don’t douche. Your vagina doesn’t require cleansing other than normal bathing. Frequent douching disrupts the vaginal balance and may increase your risk of vaginal infection. Douching won’t clear up a vaginal infection.
• Avoid a sexually transmitted infection. Use a male latex condom, limit your number of sex partners or abstain from intercourse to minimize your risk of a sexually transmitted infection.

Bacterial vaginosis diagnosis

Before you see a doctor or nurse for a test:

• Don’t douche or use vaginal deodorant sprays. They might cover odors that can help your doctor diagnose bacterial vaginosis. They can also irritate your vagina.
• Make an appointment for a day when you do not have your period.

There are tests to find out if you have bacterial vaginosis. Your doctor or nurse takes a sample of vaginal discharge. Your doctor or nurse may then look at the sample under a microscope, use an in-office test, or send it to a lab to check for harmful bacteria. Your doctor or nurse may also see signs of bacterial vaginosis during an exam.

Bacterial vaginosis can be diagnosed by the use of clinical criteria (i.e., Amsel’s Diagnostic Criteria) ⁶⁴ or Gram stain. A Gram stain (considered the gold standard laboratory method for diagnosing bacterial vaginosis) is used to determine the relative concentration of lactobacilli (i.e., long Gram-positive rods), Gram-negative and Gram-variable rods and cocci (i.e., Gardnerella Vaginalis, Prevotella, Porphyromonas, and peptostreptococci), and curved Gram-negative rods (i.e., Mobiluncus) characteristic of bacterial vaginosis. Clinical criteria require three of the following symptoms or signs:

• homogeneous, thin, white discharge that smoothly coats the vaginal walls;
• clue cells (e.g., vaginal epithelial cells studded with adherent coccobacilli) on microscopic examination (see Figure 3);
• pH of vaginal fluid >4.5 (a vaginal pH of 4.5 or higher is a sign of bacterial vaginosis); or
• a fishy odor of vaginal discharge before or after addition of 10% potassium hydroxide (i.e., the Whiff test).

Detection of three of these criteria has been correlated with results by Gram stain ⁶⁵. Other tests, including Affirm VP III (Becton Dickinson, Sparks, MD), a DNA hybridization probe test for high concentrations of Gardnerella Vaginalis, and the OSOM bacterial vaginosis Blue test (Sekisui Diagnostics, Framingham, MA), which detects vaginal fluid sialidase activity, have acceptable performance characteristics compared with Gram stain. Although a prolineaminopeptidase card test is available for the detection of elevated pH and trimethylamine, it has low sensitivity and specificity and therefore is not recommended. Polymerase chain reaction (PCR) has been used in research settings for the detection of a variety of organisms associated with bacterial vaginosis, but evaluation of its clinical utility is still underway. Detection of specific organisms might be predictive of bacterial vaginosis by polymerase chain reaction (PCR) ⁶⁶. Additional validation is needed before these tests can be recommended to diagnose bacterial vaginosis. Culture of Gardnerella Vaginalis is not recommended as a diagnostic tool because it is not specific. Cervical Pap tests have no clinical utility for the diagnosis of bacterial vaginosis because of their low sensitivity and specificity.

Although multiple nucleic acid amplification tests (NAATs) are commercially available for diagnosing bacterial vaginosis in symptomatic women, only two of these are cleared by the United States Food and Drug Administration (FDA): BD MAX Vaginal Panel and Aptima BV ⁶⁷, ⁶⁸. These tests are currently intended only for use in women with vaginitis symptoms, and can be run using a self-obtained or clinician-collected vaginal swab specimens, with results available within 24 hours ⁶⁹.

• BD MAX Vaginal Panel: The BD MAX Vaginal Panel is a multiplex, real-time polymerase chain reaction (PCR) assay used to evaluate women with vaginitis symptoms. This assay can detect major Lactobacillus species that are present in a healthy vaginal microbiota (L. crispatus, L. gasseri, and L. jensenii) and prominent bacterial vaginosis-associated bacteria (G. vaginalis, A. vaginae, BVAB-2, and Megasphaera type 1) ⁶⁷. In addition, the BD MAX Vaginal Panel can detect organisms responsible for causing trichomoniasis and vulvovaginal candidiasis ⁶⁸. This assay bases the diagnosis of bacterial vaginosis on the relative concentrations of the healthy Lactobacillus species and the bacterial vaginosis-causing organisms, with a final determination based on a proprietary algorithm ⁶⁷. For the diagnosis of bacterial vaginosis, this test has a reported sensitivity with clinician-collected specimens of 90.5% and specificity of 85.8%; similar results were seen with self-obtained specimens ⁶⁸.
• Aptima BV Test: The Aptima BV test can be used in symptomatic women to detect certain Lactobacillus species (L. Crispatus, L. gasseri and L. jensenii) and bacterial vaginosis-associated bacteria (G. vaginalis and A. vaginae). This test has a reported sensitivity with clinician-collected specimens of 95.0% and specificity of 89.6%; similar results were seen with self-obtained specimens ⁷⁰.

Bacterial vaginosis treatment

Treatment is recommended for women with symptoms ⁶⁷. The established benefits of therapy in nonpregnant women are to relieve vaginal symptoms and signs of infection. Other potential benefits to treatment include reduction in the risk for acquiring Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, HIV, and herpes simplex type 2 ⁷¹. The use of probiotics that target vaginal repletion of Lactobacillus species is an attractive concept for treatment and for prevention of recurrences, but this strategy is not recommended as a primary or adjunctive therapy for the treatment of bacterial vaginosis at this time ⁷², ⁶⁷.

Bacterial vaginosis medication

Recommended antibiotics for bacterial vaginosis ⁶⁷:

• Metronidazole 500 mg orally twice a day for 7 days;
• OR
• Metronidazole gel 0.75%, one full applicator (5 g) intravaginally, once a day for 5 days;
• OR
• Clindamycin cream 2%, one full applicator (5 g) intravaginally at bedtime for 7 days.

Accumulating reports have refuted prior warnings that metronidazole (or tinidazole) causes a disulfiram reaction in persons who ingest alcohol while taking these antibiotics ⁷³. Accordingly, experts now consider it unnecessary for persons to refrain from ingesting alcohol when they are taking metronidazole or tinidazole ⁷³, ⁶⁷.

Clindamycin cream is oil-based and might weaken latex condoms and diaphragms for 5 days after use (refer to clindamycin product information for additional information).

Women should be advised to refrain from sexual activity or use condoms consistently and correctly during the bacterial vaginosis treatment regimen. Douching might increase the risk for relapse, and no data support the use of douching for treatment or relief of symptoms.

Intravaginal clindamycin cream is preferred in case of allergy or intolerance to metronidazole or tinidazole. Intravaginal metronidazole gel can be considered for women who are not allergic to metronidazole but do not tolerate oral metronidazole.

Alternative bacterial vaginosis medicine ⁶⁷:

• Tinidazole 2 g orally once daily for 2 days;
• OR
• Tinidazole 1 g orally once daily for 5 days;
• OR
• Clindamycin 300 mg orally twice daily for 7 days;
• OR
• Clindamycin ovules 100 mg intravaginally once at bedtime for 3 days
  • Note: Clindamycin ovules use an oleaginous base that might weaken latex or rubber products (e.g., condoms and vaginal contraceptive diaphragms). Use of such products within 72 hours following treatment with clindamycin ovules is not recommended.
• OR
• Secnidazole 2 g oral granules in a single dose
  • Note: Oral granules should be sprinkled onto unsweetened applesauce, yogurt, or pudding before ingestion. A glass of water can be taken after administration to aid in swallowing.

Alcohol consumption should be avoided during treatment with nitroimidazoles. To reduce the possibility of a disulfiram-like reaction, abstinence from alcohol use should continue for 72 hours after completion of tinidazole.

Alternative regimens include several tinidazole regimens ⁷⁴ or clindamycin (oral or intravaginal) ⁷⁵. An additional regimen includes metronidazole (750-mg extended release tablets orally once daily for 7 days); however, data on the performance of this alternative regimen are limited.

Certain studies have evaluated the clinical and microbiologic efficacy of using intravaginal lactobacillus formulations to treat bacterial vaginosis and restore normal flora ⁷⁶. Overall, no studies support the addition of any available lactobacillus formulations or probiotic as an adjunctive or replacement therapy in women with bacterial vaginosis. Further research efforts to determine the role of these regimens in bacterial vaginosis treatment and prevention are ongoing.

Management of Sex Partners

Data from clinical trials indicate that a woman’s response to therapy and the likelihood of relapse or recurrence are not affected by treatment of her sex partner(s) ¹⁴. Therefore, routine treatment of sex partners is not recommended. However, a pilot study reported that male partner treatment (i.e., metronidazole 400 mg orally 2 times/day in conjunction with 2% clindamycin cream applied topically to the penile skin 2 times/day for 7 days) of women with recurrent bacterial vaginosis had an immediate and sustained effect on the composition of the vaginal microbiota, with an overall decrease in bacterial diversity at day 28 ⁷⁷. Male partner treatment also had an immediate effect on the composition of the penile microbiota; however, this was not as pronounced at day 28, compared with that among women. A phase 3 multicenter randomized double-blinded trial evaluating the efficacy of a 7-day oral metronidazole regimen versus placebo for treatment of male sex partners of women with recurrent bacterial vaginosis did not find that male partner treatment reduced bacterial vaginosis recurrence in female partners, although women whose male partners adhered to multidose metronidazole were less likely to experience treatment failure ⁷⁸. Furthermore, because female sex partners are often concurrent for bacterial vaginosis status, the option of screening and treatment of female sex partners could be considered, but this approach has not been studied rigorously in clinical trials ⁷⁹.

Post-Treatment Follow-Up

Follow-up visits are unnecessary if symptoms resolve ⁶⁷. Because persistent or recurrent bacterial vaginosis is common, women should be advised to return for evaluation if symptoms recur ⁶⁷. Detection of certain bacterial vaginosis-associated organisms has been associated with antimicrobial resistance and might be predictive of risk for subsequent treatment failure ⁸⁰. Limited data are available regarding optimal management strategies for women with persistent or recurrent bacterial vaginosis. Using a different recommended treatment regimen can be considered in women who have a recurrence; however, retreatment with the same recommended regimen is an acceptable approach for treating persistent or recurrent bacterial vaginosis after the first occurrence ⁸¹. For women with multiple recurrences after completion of a recommended regimen, 0.75% metronidazole gel twice weekly for 4–6 months has been shown to reduce recurrences, although this benefit might not persist when suppressive therapy is discontinued ⁸². Limited data suggest that an oral nitroimidazole (metronidazole or tinidazole 500 mg twice daily for 7 days) followed by intravaginal boric acid 600 mg daily for 21 days and then suppressive 0.75% metronidazole gel twice weekly for 4–6 months for those women in remission might be an option for women with recurrent bacterial vaginosis ⁸³. Monthly oral metronidazole 2g administered with fluconazole 150 mg has also been evaluated as suppressive therapy; this regimen reduced the incidence of bacterial vaginosis and promoted colonization with normal vaginal flora ⁸⁴.

HIV Infection

Bacterial vaginosis appears to recur with higher frequency in women who have HIV infection ⁸⁵. Women with HIV who have bacterial vaginosis should receive the same treatment regimen as those who do not have HIV infection.

Metronidazole (or Tinidazole) Allergy or Intolerance

For women who are allergic or intolerant to metronidazole (or tinidazole), the preferred option is to treat with clindamycin cream—one full applicator (5 grams) intravaginally at bedtime for 7 days ⁶⁷. Intravaginal metronidazole gel can be considered for women who are not allergic to metronidazole but do not tolerate oral metronidazole.

Treatment of pregnant women with symptomatic bacterial vaginosis

All pregnant women who have symptomatic bacterial vaginosis should receive treatment since symptomatic bacterial vaginosis is clearly associated with adverse pregnancy outcomes including premature rupture of membranes, preterm birth, intra-amniotic infection, and postpartum endometritis ²⁷, ²⁸. Furthermore, treating symptomatic bacterial vaginosis in pregnancy reduces symptoms and may reduce certain adverse obstetrical outcomes, such as late miscarriage. Any of the recommended bacterial vaginosis treatments for nonpregnant women (oral metronidazole, metronidazole gel, and clindamycin cream) as well as certain alternative regimens (oral clindamycin and clindamycin ovules) can be used to treat women with symptomatic bacterial vaginosis during pregnancy ⁶⁷. Metronidazole crosses the placenta and is excreted in breast milk, but it has not been linked to teratogenic effects ⁸⁶. Tinidazole is not recommended during pregnancy due to evidence of fetal harm in animal studies. There are insufficient data in pregnancy to recommend using secnidazole in pregnant women with bacterial vaginosis. Several specific preparations should not be used during pregnancy, including metronidazole 1.3% vaginal gel, the 750-mg vaginal metronidazole tablets, and the Clindesse brand of 2% clindamycin vaginal cream, which is a high-dose single application treatment for bacterial vaginosis. For breastfeeding mothers with symptomatic bacterial vaginosis, metronidazole can be used ⁶⁷.

Management of pregnant women with asymptomatic bacterial vaginosis in pregnancy

Since routine screening for bacterial vaginosis is not recommended for pregnant women who do not have vaginal symptoms, the need to address the treatment of asymptomatic bacterial vaginosis during pregnancy should not routinely arise. Available data suggest no benefit for the treatment of asymptomatic bacterial vaginosis in pregnant women who are considered at low risk for preterm delivery ⁸⁷. For pregnant women at high risk for preterm delivery (i.e., those with a previous preterm birth or late miscarriage), the impact of treating asymptomatic bacterial vaginosis is not clear and available data are conflicting—four studies showed benefit with treatment ⁸⁸, ⁸⁹, ⁹⁰, ⁹¹, two showed no benefit ⁹², ⁹³ and one showed harm ⁹⁴.

Treatment of asymptomatic bacterial vaginosis among pregnant women at low risk for preterm delivery has not been reported to reduce adverse outcomes of pregnancy in a large multicenter randomized controlled trial ⁸⁷. Therefore, routine screening for bacterial vaginosis among asymptomatic pregnant women at high or low risk for preterm delivery for preventing preterm birth is not recommended.

Treatment in women with HIV

Women with HIV experience higher prevalence and longer persistence of bacterial vaginosis compared to women without HIV ⁹⁵. The treatment of bacterial vaginosis in women with HIV should be the same as for women without HIV ⁶⁷.

Treatment of Recurrent Bacterial Vaginosis

Bacterial vaginosis recurs in approximately 30% of women within the first 3 months following treatment, and in up to 50% of women after 6 to 12 months ⁹⁶. Very little is known about antimicrobial resistance with pathogens that cause bacterial vaginosis, although clinical experience suggests that treatment failure from true antimicrobial resistance is uncommon ¹⁰.

• Single Recurrence: Women with a single recurrence can be treated with either the same recommended regimen or a different recommended regimen ⁶⁷.
• Multiple Recurrences: For women who experience multiple recurrences of bacterial vaginosis after completing treatment with a recommended regimen, a different approach from the initial treatment is recommended. Based on available data, the following regimens are suggested as options for these women ⁶⁷:
  • Metronidazole gel (0.75%) vaginal suppository twice weekly for at least 3 months ⁹⁷.
  • Metronidazole 750 mg vaginal suppository twice weekly for at least 3 months ⁹⁸.
  • Metronidazole 500 mg orally twice daily (or tinidazole 500 mg orally twice daily) for 7 days, followed by intravaginal boric acid 600 mg daily for 21 days, followed by suppressive therapy with intravaginal metronidazole gel (0.75%) twice weekly for 4 to 6 months ⁹⁹.
  • Metronidazole 2 grams orally once per month plus fluconazole 150 mg orally once per month given over a 12-month timeframe has also been evaluated as periodic presumptive therapy; this approach resulted in fewer episodes of bacterial vaginosis in one study when compared to placebo ¹⁰⁰.
  • Astodrimer 1% gel (a dendrimer-based microbicide) at a dose of 5 grams vaginally every other day for 16 weeks ¹⁰¹.

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