Research Highlights: The Effect of Oral Bacteria on Vaginal Microbiome

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The Effect of Oral Bacteria on Vaginal Microbiome

  • Bacteria are normally present in healthy vaginas.
  • Imbalances of the various types of bacteria in the vagina can lead to an infection called bacterial vaginosis (BV).
  • Women with BV are more likely to be populated by possible pathogens which includes Fusobacterium nucleatum.
  • Fusobacterium nucleatum is an oral commensal pathogen linked with a wide range of human diseases.
  • Fusobacterium nucleatum plays a role in periodontal disease and also linked with intrauterine infection and preterm birth.
  • However, the conditions and mechanisms supporting pathogen colonization during microbial imbalances of the vagina remain unclear.
  • Sialidases are group of enzymes which mainly catalyses the splitting of terminal sialic acids from complex carbohydrates on glycoproteins or glycolipids.
  • The study demonstrates that sialidase activity promoted Fnucleatum food obtaining and growth on mammalian sialoglycans.
  • Sialoglycans is a nutrient resource that was otherwise not accessible because of the lack of endogenous Fnucleatum sialidase.
  • In mice with sialidase-producing vaginal microbes, mutant Fnucleatum unable to consume sialic acids was weakened in vaginal colonization.
  • The experiments in mice also discovered that Fnucleatum may also help back to the community by fortifying sialidase activity which is a biochemical feature of human dysbiosis.
  • Using human vaginal microbiome, the study show that Fnucleatum assisted strong outgrowth of Gardnerella vaginalis.
  • Gardnerella vaginalis is a major sialidase producer and one of the most plentiful organisms in BV.
  • The results explain that mutually beneficial relationships between vaginal bacteria support pathogen colonization and may help maintain features of microbial imbalances.
  • The findings challenge the dogma that the absence of healthy lactobacilli is the sole mechanism that creates an allowable environment for pathogens during microbial imbalances of the vagina.
  • Given that Fnucleatum are common in the human mouth, the study also suggests a possible mechanism underlying links between microbial imbalances of the vagina and oral sex.


Agarwal K, Robinson LS, Aggarwal S, Foster LR, Hernandez-Leyva A, Lin H, et al. (2020) Glycan cross-feeding supports mutualism between Fusobacterium and the vaginal microbiota. PLoS Biol 18(8): e3000788.

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