New research from the Washington University School of Medicine points to a common species of bacteria as an important contributor to vaginosis, a condition linked to preterm birth and increased risk of STDs. Bacterial vaginosis affects one in every three women, but it often does not cause significant symptoms, leaving many women unaware they have it. "Bacterial vaginosis can precipitate significant health problems, but it is not a common topic of conversation between patients and their gynecologists," says researcher Amanda Lewis.
Bacterial vaginosis occurs when the typical mix of microbes in the vagina is knocked off-kilter. In some cases, bacterial vaginosis causes a change in the consistency of vaginal fluids and an unpleasant odor. The condition is diagnosed through examination of the vagina and tests of the vaginal fluids. Doctors typically treat it with antibiotics, but the condition often recurs.
Dozens of bacterial species have been linked with bacterial vaginosis, leading to heated debates in the scientific community over which bacteria actually cause the condition and its complications. The new research provides evidence that a single organism, Gardnerella vaginalis, is likely the cause.
Working with mice to simulate this condition, the researchers showed that G. vaginalis causes increased shedding of the outermost cells covering the vaginal lining. "We think the vaginal lining is shed as part of the body's effort to eliminate bacteria," explained co-researcher Nicole Gilbert. "However, this shedding may also expose sensitive underlying tissues. This may be important for understanding why women with bacterial vaginosis are more susceptible to sexually transmitted diseases and urinary tract infections."
Based on their observations in mice, the researchers compared vaginal samples from women with and without bacterial vaginosis and found that the outermost cells from the lining of the vagina are shed in higher numbers during bacterial vaginosis.
"This is the first time, to our knowledge, that the presence of increased numbers of shed cells has been detected in bacterial vaginosis in humans," Lewis says. "These results also suggest that G. vaginalis is the cause of this increase."
The researchers then examined the ability of G. vaginalis to degrade mucus, which normally helps protect the vagina and uterus from infection. The research team showed that the bacterium not only breaks up mucus barriers but also makes a meal of some of the components it frees from the barriers.
"This is the first time that a bacterium associated with vaginosis has been shown to participate in mucus degradation," says Lewis. "This is significant because infection of the uterus is a common cause of preterm birth and likely requires degradation of the mucus plug, a physical structure that protects the pregnant uterus from bacteria in the vagina."
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Source: Washington University School of Medicine