Infectious Diseases

Bacterial vaginosis

OVERVIEW: What every practitioner needs to know about bacterial vaginosis

Are you sure your patient has bacterial vaginosis? What should you expect to find?

  • Of all the clinical manifestations of bacterial vaginosis, it should be emphasized that at least half the women with bacterial vaginosis (BV) are asymptomatic.

  • When symptomatic they complain of a malodorous vaginal discharge.

    • The discharge may be minimal to fairly copious.

    • The malodor is frequently described as fishy, but this is not uniformly described.

    • The malodor tends to be worse during menses or may frequently start after menses.

    • Typical of the malodor is worsening after unprotected vaginal intercourse.

  • There is nothing on physical examination that allows a confident diagnosis be made by simply observing the discharge

    • Described as white, adherent and fairly frothy.

How did the patient develop bacterial vaginosis?

BV is now widely recognized as the commonest cause of vulvovaginal symptoms in women worldwide and affecting women in all strata of society,

  • In many epidemiologic studies, BV occurs at twice as frequently as Candida vulvovaginitis (VVC).

  • The causation of BV is highly complex and in spite of considerable progress in the study of the vaginal microbiome, pathogenesis remains unclear.

    • Microbiome studies clearly document what has been known for three decades, namely that so called protective Lactobacillus species namely L. crispatus and L. jensenii are absent or markedly reduced in women with bacterial vaginosis.

    • Lactobacillus iners, a relatively difficult organism to grow in vitro and previously unrecognized, is often present in bacterial vaginosis although its causal role is unclear.

    • With the disappearance of the aforementioned Lactobacillus species, there is an overgrowth of anaerobic microorganisms which constitute a polymicrobial vaginal microbiome which is characterized by excessive production of polyamines in particular trimethylamine.

    • Bacterial vaginosis is further associated with the creation of a vaginal biofilm on the surface of the epithelial cells and within the biofilm G.vaginalis and to a lesser extent Atopobium vaginae organisms can be found.

      • Of note, these organisms within the biofilm appear to be protected from both intravaginal as well as systemic, anti-anaerobic agents and might actually have higher MIC's in this environment.

      • The biofilm may be responsible for persistence of the organisms in the vagina and the high recurrence rate following conventional therapy.

  • Although controversial, there is strong evidence based on multiple studies worldwide in the last 5-10 years, indicating the sexual transmission of BV associate microorganisms.

    • Microbiologic studies identifying BV associated pathogens in the male urethra, the coronal sulcus and under the foreskin. Thus, sexual transmission undoubtedly occurs.

    • Epidemiologic data in lesbian populations reveal similar supportive evidence. Sexual couples are almost invariably found to have almost identical vaginal microbiomes indicating exchange of vaginal secretions.

  • It is important to recognize that while sexual transmission may be important in the initiation of BV, sexual transmission may have a much smaller role in recurrent disease, which may reflect relapse rather than reinfection.

Which individuals are of greater risk of developing bacterial vaginosis?

  • A number of epidemiologic studies have identified risk factors for acquisition of bacterial vaginosis which include:

    • Increased numbers of sexual partners

    • A recent new partner

    • Use of douching

    • Smoking

    • High frequency in certain racial groups including African Americans

    • The exact triggering mechanism for bacterial vaginosis is, however, unknown.

Beware: there are other diseases that can mimic bacterial vaginosis:

  • A similar discharge may be present in Trichomoniasis and candidiasis

  • Trichomoniasis can also present with a fishy but often described as an extremely unpleasant discharge.

What laboratory studies should you order and what should you expect to find?

Results consistent with the diagnosis

  • Vaginal pH is always abnormal in bacterial vaginosis whether symptomatic or asymptomatic and exceeds 4.5

    • A normal pH excludes the possibility of bacterial vaginosis

  • A sniff or whiff test is positive and represents a fishy odor after addition of a few drops of 10% KOH to the swab

  • If you are able to perform microscopy, you would observe clue cells, absence of polymorphonuclear leukocytes (PMN), as well as abnormal bacterial flora characterized by absence of rod morphotypes.

Results that confirm the diagnosis

  • AFIRM Test® is a DNA probe which reliably diagnoses Gardnerella vaginalis and hence BV.

  • The sialidase test (OSOM BV) is a rapid point of care test which reliably diagnoses BV

  • Polymerase chain reaction (PCR) testing for a variety of anaerobes including Atopobium vaginae, Megasphaera, BVAB

    • 1 or 2 tests are now widely available

    • PCR testing tends to be more expensive and may take 1-2 days to obtain a result

Should pregnant women be screened?

  • Despite the association between BV and preterm labor, routine screening for asymptomatic

    • BV is not a standard of care because interventional measures such as treatment have not consistently shown reduction in prematurity.

  • Symptomatic women in pregnancy should be treated for the symptoms per se.

What consult service or services would be helpful for making the diagnosis and assisting with treatment?

If the patient fails to respond a gynecologist should be consulted.

Key principles of therapy:

1. Anti-infective agents

Anti-infective agents (CDC Guidelines 2010)

  • Metronidazole (Flagyl) 500mg bid orally for 7 days


  • Metronidazole vaginal gel, 0.75% daily for 5 days or twice daily for 3 days


  • Clindamycin 2% topical cream or suppository daily for 5–7 days.

  • Alternative regimens

    • Tinidazole 2g orally once daily for 3 days


    • Tinidazole 1g orally daily for 5 days


    • Clindamycin 300mg orally twice daily for 7 days

In general, metronidazole therapy is less expensive, but all forms of therapy are comparable. CDC Guidelines advise against single dose therapy because of higher risk of recurrence.

Do I need to require that the patient return for a test of cure evaluation?

  • No, test of cure is not necessary. Over 90% of patients should be relieved of symptoms within a matter of days

  • Risk of recurrence is high and reaching 30% within 3 months and may reach as high as 80-90% within a year.

What is known about the high risk of recurrence?

  • Some recurrences are due to re-exposure to an infected female or male partner resulting in reintroduction of the pathogenic anaerobes.

  • The majority of recurrences are due to relapse of unknown etiology.

    • In some women, this is due to failure to reestablish a healthy lactobacillus dominant flora.

    • In others, relapse occurs in spite of achieving colonization.

What can be done for the women with recurrent bacterial vaginosis?

  • Unfortunately, there is no satisfactory solution to this common and frustrating problem.

  • Options include:

    • Switch to another class of therapy, i.e. nitroimidazole to clindamycin

    • Prolonging course of therapy beyond 7 days has not been shown to be effective

    • Consider re-treating the patient followed by some maintenance regimen including twice weekly metrogel and including a prolonged course of boric acid may be helpful.

    • For repeated recurrences, patients should be referred to an infectious disease/gynecologist specialist with experience in recurrent bacterial vaginosis

    • Make sure that recurrent symptoms following the antibiotic therapy for bacterial vaginosis is not due to Candida vaginitis with overlapping symptoms related to antibiotic induced infection.

      • yeast cultures should be obtained with each recurrence even in the absence of negative microscopy.

What should you tell the family about the patient's prognosis?

  • BV is anything but a simple nuisance infection with malodorous discharge.

  • Gynecologic complications includes:

    • post-hysterectomy cuff abscesses

    • increase risk of pelvic inflammatory disease (PID)

    • increased risk of preterm labor, prematurity and chorioamnionitis

  • Increased risk of urinary tract infection (UTI)

  • Increased risk of transmission of HIV to male partner and also puts female patient at increased risk.

  • Increased risk of acquiring sexually transmitted infections.

WHAT'S THE EVIDENCE for specific management and treatment recommendations?

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Fethers, KA, Fairley, CK, Morton, A. "Early sexual experiences and risk factors for bacterial vaginosis". J Infect Dis. vol. 200. 2009. pp. 1662.

Fredricks, DN, Fiedler, TL, Marrazzo, JM. "Molecular identification of bacteria associated with bacterial vaginosis". N Engl J Med. vol. 353. 2005. pp. 1899.

Fredricks, DN, Fiedler, TL, Thomas, KK. "Targeted PCR for detection of vaginal bacteria associated with bacterial vaginosis". J Clin Microbiol. vol. 45. 2007. pp. 3270.

Hauth, JC, Macpherson, C, Carey, JC. "Early pregnancy threshold vaginal pH and Gram stain scores predictive of subsequent preterm birth in asymptomatic women". Am J Obstet Gynecol. vol. 188. 2003. pp. 831.

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Lamont, RF, Sobel, JD, Akins, RA. "The vaginal microbiome: new information about genital tract flora using molecular based techniques". BJOG. vol. 118. 2011. pp. 533.

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McDonald, HM, Brocklehurst, P, Gordon, A. "Antibiotics for treating bacterial vaginosis in pregnancy". Cochrane Database Syst Rev. 2007. pp. CD000262.

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Riggs, MA, Klebanoff, MA. "Treatment of vaginal infections to prevent preterm birth: a meta-analysis". Clin Obstet Gynecol. vol. 47. 2004. pp. 796.

Schwebke, JR, Desmond, RA. "A randomized trial of the duration of therapy with metronidazole plus or minus azithromycin for treatment of symptomatic bacterial vaginosis". Clin Infect Dis. vol. 44. 2007. pp. 213.

Schwebke, JR, Desmond, R. "A randomized trial of metronidazole in asymptomatic bacterial vaginosis to prevent the acquisition of sexually transmitted diseases". Am J Obstet Gynecol. vol. 196. 2007. pp. 517.e1.

Schwebke, JR, Desmond, RA. "Tinidazole vs metronidazole for the treatment of bacterial vaginosis". Am J Obstet Gynecol. vol. 204. 2011. pp. 211.e1-6.

Senok, AC, Verstraelen, H, Temmerman, M, Botta, GA. "Probiotics for the treatment of bacterial vaginosis". Cochrane Database Syst Rev. vol. 7. 2009. pp. CD006289.

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Verstraelen, H, Verhelst, R, Nuytinck, L. "Gene polymorphisms of Toll-like andrelated recognition receptors in relation to the vaginal carriage of Gardnerella vaginalis and Atopobium vaginae". J Reprod Immunol. vol. 79. 2009. pp. 163.

Wiesenfeld, HC, Hillier, SL, Krohn, MA. "Bacterial vaginosis is a strong predictor of Neisseria gonorrhoeae and Chlamydia trachomatis infection". Clin Infect Dis. vol. 36. 2003. pp. 663.

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