The normal vaginal flora is dominated by Lactobacillus species, which produce substances that help control the growth of pathogens. Bacterial vaginosis is a clinical condition that results in a decrease of the Lactobacillus species and an increased growth of anaerobic and mycoplasma bacteria. Bacterial vaginosis has been associated with the development of pelvic inflammatory disease and preterm labor. Some studies have suggested that patients with bacterial vaginosis may be at increased risk for acquiring sexually transmitted diseases (STDs), including human immunodeficiency virus (HIV) infection. Martin and colleagues examined the association between vaginal flora and the acquisition of HIV and other STDs.

The trial was a prospective cohort study of prostitutes who attended an STD clinic for routine check-ups. Participants were given a structured interview, a physical examination, a pelvic examination and STD screening. They were followed monthly with an interview to discuss interim sexual behavior, condom use and physical symptoms. They were also reassessed at follow-up visits with a physical examination, STD screening and HIV serologic testing. A wet preparation and a potassium hydroxide (KOH) preparation were used to evaluate the vaginal secretions. Vaginal Gram stains and anaerobic cultures were obtained as well.

The study included 657 women. The mean follow-up time was 6.4 months, and the mean number of follow-up visits was three. Lactobacilli bacteria were isolated in 26 percent of women at enrollment and follow-up visits. Bacterial vaginosis was diagnosed in approximately one third of the participants. Normal vaginal flora were present in approximately one third of the participants. The absence of vaginal lactobacilli on culture was associated with an increased risk for acquiring HIV. The presence of abnormal vaginal flora increased the risk for HIV and Trichomonas infections.

The authors conclude that the lack of lactobacilli or the presence of organisms consistent with bacterial vaginosis increases the risk of acquiring HIV and other STDs. The authors note that by treating bacterial vaginosis and developing methods that promote the growth of lactobacilli in the vagina, the acquisition of HIV and STDs in women can be reduced.