Dose-dependent preventive effect of Lactobacillus reuteri CRL 1324 on Group B Streptococcus vaginal colonization in an experimental mouse model

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

Paris

Congreso; 2nd World Congress on Targeting Microbiota. Towards Clinical Revolution; 2014

Institute Pasteur

Maternal Group B Streptococcus (GBS) colonization continues to be one of the most important risk factors for developing disease in newborns, which is also promoted by increasing antibiotic resistance. Therefore, some prevention strategies that include the use of beneficial lactic acid bacteria to restore the vaginal microbial equilibrium should be developed to replace or improve antibiotic therapies. The preventive effect of different intravaginal (i.va.) doses of Lactobacillus reuteri CRL 1324 (CRL1324), a strain isolated from human vagina, showing beneficial characteristics, against vaginal colonization by GBS in a murine experimental model was evaluated in this work. The major virulence factors of four human vaginal GBS clinical isolates were determined in order to select the most virulent strain to set up a murine model of streptococcal vaginal colonization. Later, the effect of four and seven doses of 108 viable cells of CRL1324 i.va. administered prior to the GBS challenge was studied. Seven doses of CRL1324 were able to significantly reduce the number of viable GBS cells, while four doses showed no preventive effect. Both lactobacilli doses reduced the leukocyte influx induced by GBS, evaluated through cytological and histological methods. Seven doses caused a slight increase in the vaginal colonization of CRL1324, compared with four doses, and reduced murine vaginal pH compared to control mice. Moreover, CRL1324 (7 doses) caused an increase of the number of viable lactic acid bacteria without affecting the enterococci population, and a concomitant decrease of total enterobacteria and staphylococci, determined by culture-dependent methods. The results obtained in the mouse experimental model indicate that L. reuteri CL 1324 could be a promising candidate for its inclusion in probiotic products for protection against GBS in women, which could prevent GBS infections in newborns. However, further studies on the effect of L. reuteri CRL 1324 on the typical clinical situation with an established GBS colonization, and on the neonatal transmission are required.