Stay It with Flora: Maintaining Vaginal Health as a Possible Avenue for Prevention of Human Immunodeficiency Virus Acquisition

mucosal surface, the vagina may be colonized by a variety of bacteria, fungi, and other potential pathogens. A normal vaginal flora is predominately composed of Lactobacillus species, with low diversity [1]. Lactobacilli provide significant health benefits to the host by decreasing the vaginal pH through lactic acid production, generating H2O2 and bacteriocins, and stimulating the local immune system [2], all of which serve as barriers to pathogens. Thus, an abnormal vaginal flora may have significant implications for the transmission of human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs). It is therefore unfortunate that, in the real world, a normal (i.e., lactobacilli-predominant) vaginal flora is not the norm. The composition of the vaginal flora within a population constitutes a spectrum. In some individuals, H2O2producing Lactobacillus species predominate, whereas in others, the flora may include an increasing proportion of various species, such as Gardnerella vaginalis, Mycoplasma hominis, and gramnegative and gram-positive anaerobes, including Prevotella organisms [1, 3]. This spectrum is often quantified numerically by means of the Nugent scoring system, with flora classified as normal, intermediate, or bacterial vaginosis [4]. On the basis of this system, the vaginal flora is actually abnormal (i.e., it is classified as intermediate or vaginosis) in at least half of women. This abnormal status