Vaginal Diseases

Normal Vaginal Flora

All outer surfaces of the human body contain a population of bacteria known as the normal flora. These bacteria are also called commensals. Normal flora colonize the human skin, gastrointestinal tract, and other mucous membranes that may readily come in contact in the environment. This includes the vaginal area. In general, normal flora act to benefit the host by colonizing the host surfaces to exclude potential pathogens and by stimulating the host immune system.

A healthy vagina will typically contain normal flora consisting of Lactobacillus sp., Staphylococcus epidermidis, other Gram-positive cocci, Neisseria sp., various members of the Enterobacteriaceae family, and some Mycoplasma species. Lactobacillus sp. (especially Lactobacillus acidophilus in particular) are most commonly associated with normal vaginal flora and these bacteria play a key role in producing acids and reducing the vaginal pH. These conditions help to inhibit the growth of potential pathogens, thereby making the vagina a less hospitable environment for those potential pathogens. A decline in normal vaginal flora or an increase in vaginal pH, due to either the administration of antibiotics or any other reason, is thought to be a contributing factor for the onset of vaginal infections.

Bacterial Vaginosis

Bacterial vaginosis is thought to be caused by bacterial species that are normally found in low numbers in a healthy vagina as part of the normal vaginal flora. Among women of childbearing age, bacterial vaginosis is the most common cause of vaginitis and it is the most frequent reason that women in the United States visit their physician. The Centers for Disease Control and Prevention (CDC) estimates that as many as 16 percent of pregnant women have a bacterial vaginosis infection in the United States each year.

The most common causes of bacterial vaginosis are overgrowth by the following bacterial species: Gardnerella vaginalis, Bacteroides sp., Mycoplasma hominis, Ureaplasma urealyticum, and anaerobic bacteria such as Mobiluncus sp. and Prevotella species. The specific causes of bacterial vaginosis are not clear; however, activities or behaviors that upset the normal balance of bacterial normal flora in the vagina put women at increased risk. These risk activities and behaviors may include having a new sex partner or multiple sex partners, douching, and/or the use of an intrauterine device (IUD) for contraception.

...