Background: Lactobacilli are the dominant bacteria in the healthy vaginal tract, preventing the income
of pathogenic microorganisms, either sexually or not transmitted. Probiotics are used to restore the vaginal microbiome
by local administration. However, the ascendant colonization is proposed as a way to restore the vaginal
balance, and to exert some complementary effects on the host, situation that requires that probiotic strains resist
the gastrointestinal tract passage.
Objective: To determine which probiotic vaginal strains were able to resist different gastrointestinal factors (pH,
bile salts, and enzymes) to advance in the design of oral formulas.
Methods: Different protocols were applied to evaluate the growth of 24 beneficial vaginal lactic bacteria (BVL)
strains at low pH and high bile salts (individually evaluated) and in combined protocols. The viability of the
strains in simulated gastrointestinal tract conditions was studied to select the most resistant strains.
Results: A low number of BVL was able to grow at low pH. Most of the strains did not survive at high bile salts
concentration. The passage through pH first and bile salts later showed that only three strains were able to survive.
In the simulated intestinal conditions, only Lactobacillus gasseri CRL1290, L. jensenii CRL1313, and L.
jensenii CRL1349 decrease one or two logarithmic growth units (UFC/ml) at the end of the assay, maintaining
their beneficial properties.
Conclusion: The behavior of BVL in the conditions assayed is not related to specific strain or metabolic group,
because the resistance is strain-specific. The results highlight the importance of the screening performed in a way
to select the most adequate strains to be included in the oral designed formula for the restoration of the vaginal