Bacterial vaginosis pathophysiology
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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.
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.
Bacterial vaginosis is characterized by the absence of inflammation, though the following are observed:
- Slight increase in interleukin 1
- Low production of interleukin 8, preventing the attraction of macrophages and neutrophils
- Less than 10 leukocytes per epithelial cell
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. 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.
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.
Bacterial vaginosis is not considered a sexually transmitted disease, although sexual activity has been associated with development of this condition.
- Preterm birth
- Spontaneous abortion
- Pelvic inflammatory disease
- Acquisition and transmission of several sexually transmitted agents
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