In vitro probiotic properties of Lactobacillus fermentum SK5 isolated from vagina of a healthy woman

A lactobacillus strain isolated from a vaginal tract of a healthy woman was examined in vitro for its probiotic potential. This strain, identified as Lactobacillus fermentum SK5, was able to survive at pH 3-4 and 0.1-0.2% bile, and unaffected by pepsin (3 g l−1) and pancreatin (1 g l−1), but was susceptible to all tested antibiotics except metronidazole. L. fermentum SK5 had an antimicrobial potential against gastrointestinal pathogenic Escherichia coli and vaginal pathogenic Gardnerella vaginalis. The effective substance was suspected to be a bacteriocin-like compound with a molecular weight of more than 10 kDa, but hydrogen peroxide was also detected. Further studies revealed that L. fermentum SK5 had good autoaggregation characteristic and a high surface hydrophobicity that enhanced its adhesion ability to epithelial cells and for biofilm formation. This lactobacillus showed coaggregation with E. coli and G. vaginalis to affect their adhesion and colonization. The adhesion of L. fermentum SK5 to HeLa, HT-29 and Caco-2 cells and its inhibition of E. coli and G. vaginalis adherence to these cells were demonstrated. These incidences provided evidence of the possible colonization of L. fermentum SK5 that would prevent binding and growth of E. coli and G. vaginalis onto intestinal and vaginal epithelial cells. On the basis of the ability of L. fermentum SK5 to inhibit pathogenic microorganisms through coaggregation and antimicrobial substances, it is likely that this lactobacillus strain could be a potential probiotic candidate for beneficial use in protecting against gastrointestinal and vaginal microbial infections.