IN VITRO AND IN VIVO EFFECTS OF BENEFICIAL VAGINAL LACTOBACILLI ON PATHOGENIC Streptococcus agalactiae.

DE GREGORIO PRISCILLA ROMINA; JUÁREZ TOMÁS MARÍA SILVINA; NADER-MACÍAS MARÍA ELENA FÁTIMA

Tucumán

Simposio; IV Simposio Internacional de Bacterias Lácticas (SIBAL) Alimentos, Salud y Aplicaciones; 2013

Lactobacilli (Lb) are the dominant microorganisms of the vaginal microbiome of healthy women. An imbalance of the urogenital tract can produce a decrease of Lb population and an increase of pathogens, meaning a higher susceptibility to infections. Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal bacterium in the vaginal tract, but acts as pathogen in susceptible hosts. GBS can cause vaginitis in adolescent and young adult populations and serious invasive infections in susceptible adult populations. In pregnant women, the presence of GBS is associated with the risk of neonatal infections (bacteremia, sepsis, pneumonia, and/or meningitis) and death. The intravaginal administration of beneficial Lb could be a novel and alternative strategy for the biological control of GBS infections. The aim of this work was to evaluate the effects of beneficial human vaginal Lactobacillus on pathogenic S. agalactiae, through in vitro and in vivo studies. In vitro associative cultures of Lb (Lactobacillus gasseri CRL1509, Lactobacillus reuteri CRL1324 or Lactobacillus salivarius CRL1328) and S. agalactiae NH17 were performed. Two Lb inoculum (106-108 CFU/ml) and one S. agalactiae (105 CFU/ml) were assayed. Bacterial growth (by optical density and number of viable bacteria), pH, lactic acid (by HPLC) and hydrogen peroxide (peroxidase chromogenic method) were quantified at different times during the culture at 37°C. In vivo studies were performed in female BALB/c mice in pseudo-estrus state. Different groups of mice were intravaginally (i.v.) inoculated with L. gasseri CRL1509, L. reuteri CRL1324 or L. salivarius CRL1328 (107-108 CFU/dose) twice a day for two days, and then challenged i.v. with S. agalactiae NH17 (5x105CFU). Results from the in vitro and in vivo studies were analyzed by ANOVA (repeated measures and general linear models).The Lb-S. agalactiae co-cultures showed a significant inhibition of the pathogen at 4h and 8h with the high and low Lb inocula, respectively. Parallel increases of lactic acid and H2O2 levels were evidenced. The lowest numbers of pathogen (4-5 log units) were observed from 12 h of co-culture with L. gasseri CRL1509 and L. salivarius CRL1328. L. reuteri CRL1324 inhibited the pathogen growth (4 log units) after 24 h only with the high Lb inoculum. L. gasseri CRL1509 showed a greater inhibition of S. agalactiae being the highest lactic acid producer. L. reuteri CRL1324, strains with higher H2O2 production, inhibited S. agalactiae at lower levels, suggesting that the production of organic acid could be responsible of the pathogen inhibition. However, in the experimental murine model, no significant differences were obtained in the number of streptococci recovered from the vaginal tract of control mice and those inoculated with L. gasseri CRL1509, L. reuteri CRL 1324 or L. salivarius CRL1328. In conclusion, different results were obtained through in vitro and in vivo assays: vaginal Lb exhibited in vitro antimicrobial effects on S. agalactiae, but these effects were not evidenced in the murine model used. Despite both types of assays are required to assess the beneficial characteristics of the different strains, the definitive characterization and properties needs to be evaluated through phase I assays.