In vitro and in vivo effects of beneficial vaginal lactobacilli on pathogens responsible for urogenital tract infections

PRISCILLA DE GREGORIO; MARIA SILVINA JUAREZ TOMAS; MARIA CECILIA LECCESE TERRAF; MARIA ELENA FÁTIMA NADER

JOURNAL OF MEDICAL MICROBIOLOGY

SOC GENERAL MICROBIOLOGY

Lugar: London; Año: 2014 p. 685 - 696

0022-2615

The aim of this work was to evaluate the effects of beneficial human vaginal lactobacilli (Lb) on urogenital pathogens through in vitro and in vivo experiments. Co-aggregative and antimicrobial properties between five vaginal Lb strains and urogenital pathogens or potential pathogens (Streptococcus agalactiae, Staphylococcus aureus and Candida albicans strains) were assayed. Also, associative cultures of Lb strains and Streptococcus agalactiae were performed and bacterial growth, pH, lactic acid and H2O2 were determined at different times. Based on the results obtained, the in vivo studies were assayed in mice with Lactobacillus gasseri CRL 1509 or Lactobacillus salivarius CRL 1328 inoculated intravaginally (i.v.) and then challenged i.v. with Streptococcus agalactiae. Results were analysed by ANOVA (repeated measures and general linear models). Most of the Lb strains increased the percentage of aggregation of Streptococcus agalactiae strains. Only one strain (Lactobacillus reuteri CRL 1324) positively affected the aggregation of Staphylococcus aureus and none increased the aggregation of C. albicans. The inhibition of the growth of Streptococcus agalactiae strains by production of organic acids by lactobacilli was evidenced. The Lb?Streptococcus agalactiae co-cultures showed a significant inhibition of the pathogen after 4 h and 8 h of incubation. Parallel increases in lactic acid and H2O2 levels were observed. 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 Lb. In conclusion, vaginal Lb exhibited in vitro co-aggregative and antimicrobial effects on Streptococcus agalactiae strains, suggesting that they could be promising candidates for protection against Streptococcus agalactiae challenge. However, as these effects were not evidenced in the murine model used, further animal studies under different experimental conditions should be conducted to evaluate the preventive effect of Lb against challenge with Streptococcus agalactiae.