Preventive effect of Lactobacillus reuteri CRL1324 on Group B Streptococcus vaginal colonization in an experimental mouse model.

AIMS: To assess the preventive effect of different intravaginal (i.va.) doses of Lactobacillus reuteri CRL1324 against vaginal colonization by Group B Streptococcus (GBS) in a murine experimental model. METHODS AND RESULTS: The major virulence factors of four vaginal GBS clinical isolates were determined to select the most virulent strain and set up a murine model of streptococcal vaginal colonization. Later, the effect of four and seven doses of 10(8) viable cells of Lact. reuteri CRL1324 i.va. administered, prior to the GBS challenge was studied. Seven doses of lactobacilli were able to significantly reduce the number of viable GBS cells, while four doses showed no preventive effect. Both doses reduced the leucocyte influx induced by GBS. Seven doses caused a slight increase in the Lact. reuteri CRL1324 vaginal colonization compared with four doses and reduced murine vaginal pH compared to control mice. CONCLUSIONS: Lactobacillus reuteri CRL1324 evidenced a preventive effect on GBS vaginal colonization in an experimental mouse model. SIGNIFICANCE AND IMPACTS OF THE STUDY: Maternal GBS colonization is one of the most important risk factors for developing disease in newborns. Lactobacillus reuteri CRL1324 could be considered as a new biological agent to reduce infections caused by this micro-organism.

Phenotypic surface properties (aggregation, adhesion and biofilm formation) and presence of related genes in beneficial vaginal lactobacilli.

AIMS: To evaluate the phenotypic expression of auto-aggregation, adhesion to mucin and biofilm formation of lactobacilli isolated from human vagina and the presence of related genes. METHODS AND RESULTS: Seven different strains of three Lactobacillus species (Lactobacillus gasseri, Lactobacillus rhamnosus and Lactobacillus reuteri) were evaluated. The auto-aggregation property was determined by spectrophotometric assay and flow cytometry. Adhesion and biofilm formation were assayed by crystal violet staining. The presence of the genes encoding sortases, pilin subunits and surface proteins was evaluated by polymerase chain reactions. The two Lact. reuteri strains assayed showed high auto-aggregation, adhesion to mucin and biofilm formation ability. In these strains, the genes encoding three adhesion proteins were identified. In Lact. rhamnosus CRL (Centro de Referencia para Lactobacilos Culture Collection) 1332, pilus-encoding genes were detected. In all Lact. rhamnosus strains assayed, two genes encoding for other surface proteins related to adhesion and biofilm formation were detected. CONCLUSIONS: The vaginal lactobacilli assayed exhibited phenotypic and genetic characteristics that were specific for each strain. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study on auto-aggregation, adhesion and biofilm formation of vaginal Lactobacillus strains by phenotypic and genetic assays.