Use of Continuous Culture to Model Recurrent Bacterial Vaginosis
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Bacterial vaginosis (BV) is the most common vaginal tract infection seen in women of childbearing age in primary health care. In this polymicrobial condition, an alteration of vaginal microflora occurs where the lactobacilli that are usually dominant in the healthy vaginal tract are replaced by an overgrowth of Gardnerella vaginalis and anaerobic bacteria. The cause of this ecological shift in the vaginal micro flora is incompletely understood. Previous studies conducted in this laboratory isolated the vaginally-derived bacterium Enterococcus faecium 62-6, which is antagonistic to the growth of vaginal lactobacilli. The goal of the current study was to use continuous culture to model whether established populations of bacteriocin-producing E. faecium 62-6 could prevent Lactobacillus populations from establishing in the vaginal tract. Introduction of the sensitive Lactobacillus strain, L. acidophilus 4-1, showed an initial decline in concentration following exposure to E. faecium 62-6 and its bacteriocin; however, this was followed by an increase in concentration. The initial concentration decline of strain 4-1 was not observed when strain 62-6 failed to produce its bacteriocin. Strains of LactoDacilli, resistant to the strain 62-6 bacteriocin, L. casei 62-5 and L. acidophilus 46- I, in the presence of strain 62-6 and its bacteriocin were able to establish at levels slightly lower than those observed in monoculture. These results do not unequivocally support our hypothesis that bacteriocin production is one mechanism that could prevent the establishment of vaginal lactobacilli and thus promote recurrent BV. However, the initial bacteriocin-dependent decline in concentration of sensitive lactobacilli, as observed for strain 4-1, could open a niche for the opportunistic organisms associated with BV and in this way contribute to recurrent BV.