EVALUATION OF THE INTRAVAGINAL ADMINISTRATION OF BENEFICIAL HUMAN VAGINAL LACTOBACILLI IN A MURINE EXPERIMENTAL MODEL

PRISCILLA DE GREGORIO; MARIA SILVINA JUAREZ TOMAS; VIVIANA SANTOS; MARIA ELENA FÁTIMA NADER

San Miguel de Tucuman

Congreso; VII Congreso Argentino de Microbiologia General SAMIGE del Bicentenario; 2011

SAMIGE

The female urogenital tract infections (UGTI) are the result of an imbalance of the urogenital ecosystem, resulting in a decrease of protective lactic acid bacteria (LAB). One of the alternatives proposed for the prevention and/or treatment of UGTI is the application of probiotic products containing LAB. The objectives of the present work were to evaluate the degree of colonization of vaginal lactobacilli selected by their potentially probiotic properties, and if they produce some type of adverse effect on the vaginal tract of mice. Two-months-old female BALB/c mice were inoculated intramuscularly with estradiol (48 h before the inoculation of lactobacilli), in order to induce the estrogenic phase of estrous cycle. In the first stage, five different strains of human vaginal lactobacilli (<i>Lactobacillus gasseri</i> CRL1263, <i>L. gasseri</i> CRL1509, <i>L. reuteri</i> CRL1324, <i>L. salivarius</i> CRL1328 and <i>L. rhamnosus</i> CRL1332) were intravaginally administered (10 ⁷-10⁸ CFU/50 &mu;l) to different groups of mice, two times every day during two days. The number of viable lactobacilli in vaginal washings and the production of adverse effects on vaginal tract (by standard cytological and histological techniques) were determined at 2 and 4 days post-inoculation. In the second stage, <i>L. gasseri</i> CRL1263 and <i>L. salivarius</i> CRL1328 were administered as follows: a) two inoculations every day during two days (scheme 1), or b) two inoculations every day, during four days (scheme 2). The number of viable lactobacilli was evaluated in vaginal washings and homogenates, at 2, 5 and 7 days post-inoculation. On the day 2 post-inoculation, the five strains were recovered in vaginal washings (10³-10⁴CFU/50 &mu;l). On day 4, a decrease of 1-2 logarithmic units was observed for all the strains. The inoculation of lactobacilli did not produce modifications in the histological structure of the vaginal tract; the characteristics of the different layers of the epithelial and connective tissues were similar both in control and lactobacilli-treated mice, at all the days evaluated. When the inoculation assay 1 was performed, the number of viable cells of <i>L. gasseri</i> CRL1263 and <i>L. salivarius</i> CRL1328 were around 10³ CFU/50 &mu;l (in vaginal washings) and 10³ CFU/70 mg (in homogenates). Only <i>L. salivarius</i> CRL1328 was able to persist up to day 5 in the vaginal tract, being the counts higher in vaginal washing (10² CFU/50 &mu;l) than in homogenates (10 CFU/70 mg). The administration of lactobacilli at higher doses (scheme 2) did not produce a better recuperation of bacteria in the vaginal tract. The results of this work support the safe use of beneficial vaginal lactobacilli as probiotics to restore the ecological balance of the UGT, based in the no production of adverse effects at cytological and histological levels.