361 Assessment of Nomadic and Niche-specialist Lactobacilli as Potential Vaginal Probiotics

Recent studies have shown that the microbiota during the early years of an individual’s life is affected by the mode of release during childbirth, differing between caesarean section and newborns born vaginally. Here we reported the selection of nomadic lactobacilli for the development of a multi-strain probiotic gel to promote lactobacilli-dominated vaginal microbiota in pregnant women and to establish a proper eubiosis in the new-born. Lactobacilli, mainly isolated from food sources, were screened for functional characteristics and the capability to inhibit Streptococcus agalactiae and Candida albicans, which may lead to adverse pregnancy-related outcomes. A total of ninety-five strains (Lacticaseibacillus paracasei or Lactiplantibacillus plantarum) were screened for auto-aggregation, hydrogen peroxide production, hydrophobicity, and lactic acid isomers quantification. Cell-free supernatants (CFSs) of the candidate strains were also co-inoculated with vaginal pathogens for high-throughput inhibition screening. The best performing strains were also screened in vitro, alone or in combination, on the SkinEthicTM HVE model, to evaluate the reduction of the expression of genes (interleukin-8, interleukin-6 and tumour-necrosis factor alpha) involved in the inflammatory cascade. We found that the production of hydrogen peroxide was strain-dependent, with the highest concentrations found for L. paracasei. L. plantarum produced both isomers of lactic acid, while Lb. paracasei produced only L-isomer. Hydrophobicity and auto-aggregation characteristics higher than 50% were observed respectively for 25% and 86% of all the strains. S. agalactiae was strongly inhibited by a wide range of CFSs, whereas C. albicans inhibition was less frequent. Two of the best performing strains showed a reduction in the expression of genes involved in the inflammatory cascade. Overall, L. plantarum had the highest pathogen inhibition score and the best functional traits.