Oral sex can trigger bacterial vaginosis

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Sialic acids play an essential role in maintaining bacterial growth, survival, and virulence. According to the current study hypothesis, in a condition like bacterial vaginosis, bacterial population with sialidase activity mutually facilitates the persistence of bacterial species that do not have sialidase activity.
Mutually beneficial relationship between diverse bacterial populations in the vagina

Fusobacterium nucleatum is a Gram-negative bacterium predominantly found in the human mouth. This bacterium does not have endogenous sialidase activity and is known to colonize with bacterial population that has sialidase activity. As hypothesized by the researchers, F. nucleatum may utilize sialic acids as a nutritional source in the presence of exogenous sialidases produced by sialidase-positive bacteria.

Using both in vivo and in vitro experimental models, the researchers observed that F. nucleatum cannot utilize glycan-bound sialic acids because of the absence of sialidase activity. However, upon colonization with sialidase-producing vaginal bacteria, F. nucleatum can get nutritional benefits from sialic acids. Moreover, the researchers found that F. nucleatum maintains a mutually beneficial relationship with sialidase-producing bacteria by triggering the characteristics of vaginal dysbiosis, such as increased sialidase activity and enrichment of Gardnerella vaginalis. The maintenance of vaginal dysbiosis, in turn, facilitates the persistence of susceptible bacterial population in the vagina.

Journal reference:

Agarwal K. 2020. Glycan cross-feeding supports mutualism between Fusobacterium and the vaginal microbiota. PLOS Biology. https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000788