Vaginal flora
[2] The primary colonizing bacteria of a healthy individual are of the genus Lactobacillus,[3] such as L. crispatus, and the lactic acid they produce is thought to protect against infection by pathogenic species.
[4] The primary colonizing bacteria of a healthy individual are of the genus Lactobacillus (90–95%), the most common being L. crispatus, L. iners, L. jensenii, and L.
Lactobacilli have been shown to inhibit in vitro growth of pathogenic microorganisms, e.g. Bacteroides fragilis, Escherichia coli, Gardnerella vaginalis, Mobiluncus spp., Neisseria gonorrhoeae, Peptostreptococcus anaerobius, Prevotella bivia and Staphylococcus aureus.
[5] Production of hydrogen peroxide (H2O2) is a proposed mechanism for bacterial antagonism in vitro,[16][17][18] inhibiting growth of microorganisms via direct interaction or via human myeloperoxidase.
Under optimal anaerobic growth conditions, physiological concentrations of lactic acid inactivated the BV-associated pathogens without affecting the vaginal lactobacilli.
[30] However, more recently O'Hanlon et al.[22] demonstrated that cervicovaginal fluid and semen have a significant H2O2-blocking activity and they later [12] demonstrated that physiological concentrations of H2O2 below 100 μM fail to inactivate any of the 17 tested BV-associated bacteria, e.g. A. vaginae, G. vaginalis, Mobiluncus spp., P. bivia, P. corporis, Mycoplasma hominis, even in the presence of human myeloperoxidase, known to increase the microbicidal activity of H2O2.
Possible explanations may be that cervicovaginal fluid and semen contain proteins, glycoproteins, polysaccharides, lipids, and other molecules with the potential to react with and inactivate H2O2.
[13] Lactobacillus species differ in premenopausal women, i.e. L. crispatus, L. jensenii, L. iners, L. gasseri (and possibly Limosilactobacillus vaginalis), as assessed through cultivation-dependent and cultivation-independent techniques.
[33] However, the vaginotropism, does not only apply to this selected group of lactobacilli that stand for a healthy vagina, but also for the bacterial species associated with BV.
[34] The microbiota detected in the human genital and gut econiche do not appear to grow outside their host and probably are likely to rely on the close contact between parents and their children for transmission,[34] e.g. mother to neonate transmission of genital microflora, most probably also with gut microflora homogenously distributed over the baby's body including skin, the oral cavity, nasopharynx, and feces.
[35] Bacterial vaginosis (BV) is associated with the presence of Gardnerella vaginalis and Peptostreptococcus anaerobius[36] and a decrease in the number of Lactobacillus species that comprise the healthy vaginal microbiota.
To obtain a Nugent score, gram stain techniques are carried out and it characterizes the bacterial morphology on a scale.
[26][44] Several studies have demonstrated that a significant proportion (7–33%) of healthy asymptomatic women (especially black and Hispanic women)[45] lack appreciable numbers of Lactobacillus species in the vagina,[33][46] and instead have a vaginal microbiota that consist of other lactic acid-producing bacteria, i.e. species from the genera Atopobium, Leptotrichia, Leuconostoc, Megasphaera, Pediococcus, Streptococcus and Weissella,[32][33][45] All ethnic populations have vaginal microflora communities containing lactic acid producing bacteria.
[37] A healthy vaginal microbiome aids in the prevention of bacterial vaginosis, yeast infections and other possible problems by maintaining an acidic pH (< 4.5) that is unfavourable for the growth of common pathogens, such as Gardnerella vaginalis.
The lactobacilli present in a healthy vaginal microbiome also occupy the ecological niche that would otherwise be available for exploitation by pathogenic organisms.
[54] Smoking and alcohol consumption can also increase likelihood of BV development because it indirectly impacts the metabolite production profile.
Research shows that diets rich in nutrients with low glycemic index and lower fat intake may be associated with a decreased chance of getting BV.
