Lactobacilli, the predominant vaginal microorganisms in healthy premenopausal women, control other members of the vaginal microflora and thus protect against bacterial vaginosis and urinary tract infections. It has been claimed that some lactobacilli are also protective against Candida vaginitis. Little is known, however, about the mechanisms by which these lactobacilli can control vaginal populations of Candida and prevent vaginitis. To address this question, vaginal Lactobacillus strains with known antagonistic properties against bacteria were tested for their cell surface properties, adhesion to vaginal cell lines in vitro and antagonistic activities against Candida. A small proportion of the lactobacilli tested adhered strongly to cultured vaginal epithelial cells and inhibited growth of Candida albicans but not of C. pseudotropicalis. This anticandidal activity was in some Lactobacillus strains related to hydrogen peroxide (H2O2) production, but catalase treatment did not suppress this activity in other Lactobacillus strains, suggesting alternative mechanism(s). Moreover, tested vaginal Candida strains were resistant to relatively high concentrations of H2O2 that markedly exceeded those produced by even the most active Lactobacillus strains.
Several mechanisms mediate the adherence of bacteria to host tissues, but the physical and chemical properties of the bacterial surface play a key role. Little is known about the surface properties of Lactobacillus that mediate attachment to human epithelial cell surfaces. In this study, we looked at the speci c characteristics of the surface of Lactobacillus strains. These characteristics included the effect of Lactobacillus on the hemagglutination of rabbit, sheep, bovine, guinea pig and human erythrocytes, its surface hydrophobicity, slime production and the adherence of Lactobacillus to two different epithelial cell lines. These properties were compared by using electron microscopy on the cell surface. In a few Lactobacillus strains, surface properties such as hemagglutination of human OP 1 erythrocytes, the presence of extracellular slime material and their high degree of hydrophobicity appeared to be related to one another. The most surface-active strains of Lactobacillus adhered well to both enterocytes and to vaginal cells. These characteristics seem to be closely related; however, different adhesions and various mechanisms of attachment may play a role in the adherence of different Lactobacillus strains to epithelial surfaces.
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