Evaluation of the Inhibitory Effects of Lactobacillus gasseri and Lactobacillus crispatus on the Adhesion of Seven Common Lower Genital Tract Infection-Causing Pathogens to Vaginal Epithelial Cells

Abstract

<b>Background/Purpose:</b> <i>Lactobacillus</i> colonization is important to maintain urogenital flora stability and prevent pathogenic infection. Different <i>Lactobacillus</i> species have distinct properties and effects on the urogenital flora. To select probiotics that colonize the vagina and provide protection against pathogenic infection, we evaluated the adhesion of five <i>Lactobacillus</i> strains and their inhibitory effects on the adhesion of pathogens to vaginal epithelial cells (VECs). <b>Methods and Materials:</b> (1) <i>Lactobacillus</i> adhesion experiments: VK2/E6E7 and primary VECs were used to evaluate the adhesion of two <i>Lactobacillus gasseri</i> and three <i>Lactobacillus crispatus</i> strains. The adhesion of these five <i>Lactobacillus</i> strains was compared. (2) Adhesion inhibition experiments: The inhibitory effects of the five <i>Lactobacillus</i> strains on the adhesion of pathogens (<i>Gardnerella, Mobiluncus, Candida albicans, Streptococcus agalactiae, Staphylococcus aureus, Escherichia coli</i>, and <i>Enterococcus faecalis</i>) were evaluated by adhesion exclusion, displacement, and competition experiments. <b>Results:</b> (1) <i>Lactobacillus</i> adhesion was stronger in the primary VECs than in the VK2/E6E7 VECs (<i>P</i> < 0.05). The adhesion of the three <i>L. crispatus</i> strains was stronger than that of the two <i>L. gasseri</i> strains (<i>P</i> < 0.05). <i>L. crispatus</i> 4# showed the strongest adhesion. (2) The exclusion, displacement, and competition experiments showed that all five <i>Lactobacillus</i> strains significantly inhibited the adhesion of the seven pathogenic strains to the VECs (<i>P</i> < 0.05). The displacement effect was stronger than the exclusion and competition effects of each <i>Lactobacillus</i> strain. (3) The results of the exclusion, displacement, and competition experiments indicated that <i>L. gasseri</i> 1# showed the strongest adhesion inhibition of <i>C. albicans</i> and <i>S. agalactiae</i>. <i>L. crispatus</i> 3# showed the strongest adhesion inhibition of <i>S. aureus</i>, whereas <i>L. crispatus</i> 4# showed the strongest adhesion inhibition of <i>Gardnerella, Mobiluncus, E. coli</i>, and <i>E. faecalis</i>. <b>Conclusion:</b> The source of the VECs might not affect the selection of the most adhesive <i>Lactobacillus</i> strain. <i>L. crispatus</i> showed stronger VEC adhesion than <i>L. gasseri</i>. The degree of antagonism of the <i>Lactobacillus</i> strains toward the different pathogens varied. This result provides incentives for personalized clinical treatment.