Experimental Administration of Estradiol on the Colonization of Lactobacillus fermentum and Escherichia coli in the Urogenital Tract of Mice

The effect of estrogen on the microbial colonization of the urogenital tract is widely discussed, mainly in regard to women with a high incidence of Urinary Tract Infections (UTI). The aim of this work was to study the effect of estradiol on the microbial colonization of lactobacilli and E. coli in mice. Female BALB/c mice were intramuscularly (i.m.) treated with β-estradiol (one or three doses). The next day, L. fermentum was inoculated intraurethrally with three doses of 107 CFU (Colony Forming Units). Later, mice were challenged with uropathogenic E. coli (1×108 CFU). The hormone levels in sera increased to values 10 times higher than in control animals. Increased differentiation of desquamated vaginal cells and keratinization of the vaginal surface were also observed. The hormonal treatment produced an increased E. coli colonization in the whole tract and a higher level of L. fermentum in kidneys on the 6th day. In mice treated with hormones and lactobacilli, one dose of estradiol was enough to protect animals against the challenge with E. coli. Three doses of estradiol produced a more pronounced protection with a lower number of E. coli. No histological modifications were produced by L. fermentum, while lymphocytic proliferation at submucosal level was observed in E. coli-challenged animals.