Microbial flora variations in the respiratory tract of mice

A stable microbial system in the respiratory tract acts as an important def ense mechanism against pathogenic microorganisms. Perturbations in this sys tem may allow pathogens to establish. In an ecological environment such as the respiratory tract, there are many diverse factors that play a role in t he establishment of the indigenous flora. In the present work we studied th e normal microbial flora of different areas of the respiratory tract of mic e and their evolution from the time the mice were born. Our interest was to know which were the dominant groups of microorganisms in each area, which were the first capable of colonizing and which dominated over time to be us ed as probiotic microorganisms. Our results show that Gram negative facultatively anaerobic bacilli and str ict anaerobic microorganisms were the lat ones to appear in the bronchia, w hile aerobic and Gram positive cocci were present in all the areas of the r espiratory tract. The number of facultative aerobes and strict anaerobes we re similar in the nasal passage, pharynx instilled and trachea, but lowe in bronchia. The dominant species were Streptococcus viridans and Staphylococcus saproph yticcus, followed by S. epidermidis, Lactobacilli and S. cohnii I which wer e present on every studied days but at different proportions. This paper is the first part of a research topic investigating the protecti ve effect of the indigenous flora against pathogens using the mice as an ex perimental model.