Pathogenesis of Bacterial Vaginosis in Women Who Have Sex With Women
Condition: Vaginosis, Bacterial
MeSH terms: Vaginosis, Bacterial; Vaginal Diseases
Study type: Observational

Summary: 
      The objectives of this study are to: (1) use cultivation-independent molecular methods to
      determine the sequence of microbiological events culminating in bacterial vaginosis (BV)
      among sexually active African American women who have sex with women (AAWSW) and (2)
      determine if specific Gardnerella vaginalis oligotypes are associated with the development of
      BV among sexually active AAWSW.
    

Detailed description: 
      Bacterial vaginosis (BV) is the most common cause of vaginal discharge in the U.S. It is
      associated with adverse outcomes including preterm birth, pelvic inflammatory disease, and
      increased risk of acquisition and transmission of sexually transmitted infections (STIs),
      including HIV. Microbiologically, BV is characterized by depletion of lactobacilli that
      comprise the normal vaginal flora and increases in facultative (Gardnerella vaginalis; GV)
      and strict anaerobes.

      Three out of four Amsel criteria are necessary for the clinical diagnosis of BV and include
      (1) homogeneous, thin, grayish-white vaginal discharge, (2) vaginal pH >4.5, (3) positive
      whiff-amine test, and (4) clue cells present on a wet mount of vaginal fluid. BV diagnosis,
      however, is based most rigorously on Nugent scoring of a Gram stain of vaginal secretions.
      Optimal vaginal flora, indicative of a predominance of lactobacilli, is represented by a
      Nugent score of 0-3. Abnormal vaginal flora includes not only what is currently defined as BV
      (Nugent score 7-10) but also what is referred to as intermediate flora (Nugent score 4-6).
      For reasons not well understood, BV is very common among women who have sex with women (WSW),
      perhaps more so than among heterosexual women. Risks for prevalent BV among WSW have included
      higher numbers of lifetime female sexual partners, shared use of vaginally inserted sex toys,
      and oral-anal sex. In addition, WSW in monogamous sexual partnerships have a high concordance
      for the presence or absence of BV. These data support the hypothesis that BV is sexually
      transmitted.

      It is well accepted that BV is caused by a synergistic relationship between a large number of
      microorganisms including GV and other anaerobics (i.e. BV-associated bacteria; BVAB) however
      the trigger which initiates these alterations is debated. It is unknown whether BV results
      from acquisition of GV as the "founder" organism which subsequently leads to the complex
      changes in the vaginal microbiota associated with BV or whether BV is transmitted as a
      polymicrobial consortium. GV, as a facultative anaerobe, may be better able to tolerate the
      high oxidation-reduction (redox) potential of the healthy vaginal microbiome, unlike strict
      anaerobes. Similar to facultative anaerobes involved in the initiation of oral disease, it is
      possible that GV, through its metabolic pathways and ability to form a biofilm (perhaps
      influenced by specific oligotypes), creates a lower redox potential in the vaginal
      microbiome. This alteration would then cause a marked decrease in lactobacilli and an
      increase in other BVAB that are normally present in very low concentrations, leading to the
      BV syndrome. Determining the exact etiology of the agent(s) causing a shift from optimal to
      abnormal vaginal flora and BV is vital for appropriate treatment and prevention of adverse
      outcomes. With increasing use of molecular methods, identification of vaginal microorganisms
      (some uncultivable) to the species level in women with BV has become more feasible. This
      study will seek to further investigate BV pathogenesis. We hypothesize that sexual exposure
      to Gardnerella vaginalis is the inciting event leading to the complex changes in vaginal
      flora associated with BV. If Gardnerella vaginalis is the initial insult, then its appearance
      and establishment in the vaginal microbiome will be seen in women who develop incident BV
      prior to increases in other BV-associated bacteria.

      Only African American women will be enrolled in this protocol as differences in the
      composition of vaginal microbial communities of women with and without BV of different racial
      and ethnic groups have been noted which could confound the results of this study.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Sexually active African American women who have sex with women with normal vaginal flora at
        baseline (determined based on 0/4 Amsel criteria and a normal Nugent score of 0-3 with no
        Gardnerella vaginalis morphotypes noted on vaginal Gram stain) will be followed
        prospectively over a 90 day time period for the development of incident BV.
      
Biospecimen description: 
      Self-collected vaginal swabs from women participating in this study will be stored for future
      research purposes related to the study of the vaginal microbiome.
    
Keywords: women's health; vaginosis, bacterial; african americans