Effect of lactobacilli administration in the vaginal tract of mice: evaluation of side effects and local immune response by local administration of selected strains.

Lactobacilli are the predominant microorganisms in the vaginal tract of human and some homeothermic animals. They can maintain the ecological equilibrium of the tract by protecting against pathogenic microorganisms. In the last few years, there has been an increased tendency to use probiotic microorganisms to restore the ecological equilibrium and to protect against infections. This principle has been widely applied to the gastrointestinal tract. More recently, some other studies have reported the application of probiotics in different tracts, for example, the urogenital or respiratory tract. One of the objectives of our group is to design probiotic products for the urogenital tract. With this purpose, lactobacilli were isolated from the human vagina, and later some of them were selected for their probiotic characteristics (production of antagonistic substances or adhesion capability). The application of probiotic products in the vaginal tract has been approached empirically; some pharmaceuticals containing these microorganisms are available in the United States or Europe or are protected under the patent process or intellectual property rights. There are not enough studies in humans or animals to determine whether their administration can produce some type of collateral or adverse effect. Using Balb/c mice as the experimental model, the object of the present work was to study (1) whether intravaginal administration of human lactobacilli can produce colonization of the tract; (2) whether such administration produces some type of adverse or collateral effect; and (3) whether probiotics are able to stimulate the local immune system. Keeping in mind that hormones can affect the colonization or persistence ability of microorganisms, and with the purpose of having all animals at the same point in the sexual cycle, animals were cycled with estradiol 48 h before inoculation with lactobacilli. They were then inoculated im with hormones 48 h before beginning microorganism inoculations. Later they were intravaginally inoculated with the appropriate dose of each Lactobacillus strains. The animals were sacrificed on different days after inoculation to perform the following studies: 1. Microbiological assays: To determine the number of lactobacilli in the tract (in vaginal washes or in organ homogenates), by plating the samples in selective media containing antibiotic (to differentiate the resident flora from those administered experimentally).