Bacterial vaginosis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Mehrsefat, M.D. [2]

Overview

Bacterial vaginosis is a syndrome that results from an imbalance in the different types of bacteria in the vagina (also called vaginal "flora"). The healthy vaginal microflora is comprised mainly of Gram-positive bacilli of the genus Lactobacillus. Lactobacilli play an important role in maintaining the health of the female genital tract by keeping the pH of the vagina at normal levels. When the pH levels of the vagina become unbalanced, certain microorganisms may overtake the normal flora, which can cause a low-grade infection that often produces abnormal vaginal discharge.[1][2]

Pathophysiology

Bacterial vaginosis results from the replacement of the normal, hydrogen peroxide-producing Lactobacillus spp. with high concentrations of anaerobic bacteria, Gardnerella vaginalis, Ureaplasma, and Mycoplasma in the vagina.[3]

Bacterial vaginosis is characterized by the absence of inflammation, though the following are observed:

The healthy vaginal microflora is comprised mainly of Gram-positive bacilli of the genus Lactobacillus including L. crispatus, L. iners, L. gasseri, and L. jensenii. However, other non-beneficial microbial species (e.g., Gardnerella vaginalis, Enterococcus spp., and Prevotella spp.) can be present in small numbers that are not sufficient to cause disease. Lactobacilli play an important role in maintaining the health of the female genital tract by keeping the pH of the vagina at normal levels.[1] When pH levels of the vagina become unbalanced, certain microorganisms may overtake the normal flora, causing a low-grade infection that often results in an abnormal vaginal discharge.[2]

Pathogenesis

While the exact pathogenesis of bacterial vaginosis is not fully understood, it is thought that BV is a result of an imbalance in the different types of bacteria in the vagina by following mechanisms:

  • Their is a loss of lactobacilli resulting in rising pH and massive overgrowth of vaginal anaerobes.
  • Increase in pH may results in decreased hydrogen peroxide production, which also facilitates adherence of Gardnerella vaginalis to the exfoliating epithelial cells.
  • Decrease in hydrogen-peroxide production results in overgrowth of the anaerobes.
  • Anaerobes produce large amounts of proteolytic carboxylase enzymes.
  • Proteolytic carboxylase enzymes break down vaginal peptides into a variety of amines that are volatile, malodorous, and associated with increased vaginal transudation.

It is also thought that Gardnerella vaginalis is the pathogen responsible for the initiation of bacterial vaginosis, with other pathogens acting as secondary intruders.[4]

Associated Conditions

Bacterial vaginosis is not considered a sexually transmitted disease, although sexual activity has been associated with development of this condition.

Bacterial vaginosis has been associated with such serious health problems as:[1][5][6][7]

References

  1. 1.0 1.1 1.2 Machado D, Castro J, Palmeira-de-Oliveira A, Martinez-de-Oliveira J, Cerca N (2015). "Bacterial Vaginosis Biofilms: Challenges to Current Therapies and Emerging Solutions.". Front Microbiol. 6: 1528. PMC 4718981Freely accessible. PMID 26834706. doi:10.3389/fmicb.2015.01528. 
  2. 2.0 2.1 Borges S, Silva J, Teixeira P (2014). "The role of lactobacilli and probiotics in maintaining vaginal health.". Arch Gynecol Obstet. 289 (3): 479–89. PMID 24170161. doi:10.1007/s00404-013-3064-9. 
  3. Koumans EH, Sternberg M, Bruce C, et al. The prevalence of bacterial vaginosis in the United States, 2001-2004: associations with symptoms, sexual behaviors, and reproductive health. Sex Transm Dis 2007;34:864–9.
  4. Schwebke JR, Muzny CA, Josey WE (2014). "Role of Gardnerella vaginalis in the pathogenesis of bacterial vaginosis: a conceptual model.". J Infect Dis. 210 (3): 338–43. PMID 24511102. doi:10.1093/infdis/jiu089. 
  5. Guerra B, Ghi T, Quarta S, Morselli-Labate AM, Lazzarotto T, Pilu G; et al. (2006). "Pregnancy outcome after early detection of bacterial vaginosis.". Eur J Obstet Gynecol Reprod Biol. 128 (1-2): 40–5. PMID 16460868. doi:10.1016/j.ejogrb.2005.12.024. 
  6. Rothman KJ, Funch DP, Alfredson T, Brady J, Dreyer NA (2003). "Randomized field trial of vaginal douching, pelvic inflammatory disease and pregnancy.". Epidemiology. 14 (3): 340–8. PMID 12859036. 
  7. Jacobsson B, Pernevi P, Chidekel L, Jörgen Platz-Christensen J (2002). "Bacterial vaginosis in early pregnancy may predispose for preterm birth and postpartum endometritis.". Acta Obstet Gynecol Scand. 81 (11): 1006–10. PMID 12421167. 

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