Could Probiotics Be an Option for Treating and Preventing Urogenital Infections?

Gregor Reid, PhD, MBA, Andrew W. Bruce, MD, FRCS

In This Article

What Role Do the Vaginal Flora Play in the Defense Against Urogenital Infections?

Our interest in the potential role of the "normal" vaginal flora began almost 30 years ago with our finding of low lactobacilli counts in the vagina and urethra in women suffering from recurrent UTIs.[36] This seemed to indicate that the lactobacilli formed a barrier microbial population that protected the host from infection. Thus, we hypothesized that the risk of infection would be reduced if lactobacilli were present as the dominant member of the flora. We addressed the following questions: What causes the demise of lactobacilli with resultant infection, and how could the lactobacilli numbers be increased in women depleted of their lactobacilli flora? In answer to the first question, it seems that it is disruption of the normal vaginal flora -- found in one study to be caused by broad-spectrum antibiotics (which can wipe out the flora for 1-2 months[29]), spermicides (which kill hydrogen peroxide-producing strains), hormone fluctuations (counts of lactobacilli are highest at peak estrogen levels), dietary substances (in vitro experiments suggest that vitamin C might increase lactobacilli numbers, as does skim milk inserted via syringe into the vagina), and factors not fully understood. It is now recognized that the vaginal flora fluctuate daily with regard to both the types and numbers of organisms.

One study of normal volunteers showed a marked variation in introital organisms mediated by changes in urinary frequency.[37] It is estimated that, at some point in time, up to 78% of women will have an "unhealthy" flora although they are free of symptoms.[38,39] The exact role played by lactobacilli and other commensals found in the vagina is slowly being elucidated, and their presence in a dominant mode is essential for vaginal health. Their presence on vaginal epithelial cells seems to act as a barrier to infection, but not, as initially presumed, solely by blocking adherence of pathogens. Their defensive role also depends on their survival (often in symbiosis with potential pathogens), their capability of producing such antibacterial materials as hydrogen peroxide to limit pathogen growth, their production of biosurfactants that inhibit pathogen adherence, and their ability to prime macrophages, leukocytes, cytokines, and other host defenses.[40,41,42,43]


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