A prospective cohort study was conducted to examine the relationship between vaginal colonization with lactobacilli, bacterial vaginosis (BV), and acquisition of human immunodeficiency virus type 1 (HIV-1) and sexually transmitted diseases in a population of sex workers in Mombasa, Kenya. In total, 657 HIV-1-seronegative women were enrolled and followed at monthly intervals. At baseline, only 26% of women were colonized with Lactobacillus species. During follow-up, absence of vaginal lactobacilli on culture was associated with an increased risk of acquiring HIV-1 infection (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.2-3.5) and gonorrhea (HR, 1.7; 95% CI, 1.1-2.6), after controlling for other identified risk factors in separate multivariate models. Presence of abnormal vaginal flora on Gram's stain was associated with increased risk of both HIV-1 acquisition (HR, 1.9; 95% CI, 1.1-3.1) and Trichomonas infection (HR, 1.8; 95% CI, 1.
3-2.4). Treatment of BV and promotion of vaginal colonization with lactobacilli should be evaluated as potential interventions to reduce a woman's risk of acquiring HIV-1, gonorrhea, and trichomoniasis.
The human vaginal ecosystem is dominated by Lactobacillus species [1,2]. Lactobacilli are gram-positive rods that, in vitro, produce substances with antimicrobial properties, including lactacidin, acidolin, lactacin B, and hydrogen peroxide (H 2 O 2 ) [3]. H 2 O 2 -producing lactobacillus strains play a pivotal role in controlling the microenvironment of the vagina and in inhibiting the overgrowth of potentially pathogenic organisms [3][4][5][6][7]. In vitro, H 2 O 2 -producing lactobacilli are cidal to human immunodeficiency virus type 1 (HIV-1), perhaps because of the reaction of H 2 O 2 with myeloperoxidase and halides present in vaginal fluid [8].
Bacterial vaginosis (BV) is a clinical condition that is characterized by decreased H 2 O 2 -producing lactobacilli and increased concentrations of anaerobic gram-negative rods, Gardnerella species, and genital mycoplasmas [1,7,9,10]. In some