Microbial flora variations in the respiratory tract of mice

A stable microbial system in the respiratory tract acts as an important defense mechanism against pathogenic microorganisms. Perturbations in this system may allow pathogens to establish. In an ecological environment such as the respiratory tract, there are many diverse factors that play a role in the establishment of the indigenous flora. In the present work we studied the normal microbial flora of different areas of the respiratory tract of mice 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 used as probiotic microorganisms. Our results show that Gram negative facultatively anaerobic bacilli and strict anaerobic microorganisms were the last ones to appear in the bronchia, while aerobic and Gram positive cocci were present in all the areas of the respiratory tract. The number of facultative aerobes and strict anaerobes were similar in the nasal passage, pharynx instilled and trachea, but lower in bronchia. The dominant species were Streptococcus viridans and Staphylococcus saprophyticcus, followed by S. epidermidis, Lactobacilli and S. cohnii I which were present on every studied days but at different proportions. This paper is the first part of a research topic investigating the protective effect of the indigenous flora against pathogens using the mice as an experimental model.

Estudio de resistencia de Mycobacterium tuberculosis a distintos quimioterapicos / Resistance of Mycobacterium tuberculosis to different chemoterapeutic agents

Se efectuaron estudios de susceptibilidad de 62 cepas de M. tuberculosis aisladas a partir de esputos y/o lavados bronquiales. El método usado fue el de las proporciones de Canetti-Rist-Grosset. Las drogas y concentraciones empleadas en esta técnica fueron: INH (sioniácida) = 0,2 ug/ml; RIF (rifampicina) = 20 ug/ml; SM (estreptomicina) = 4 ug/ml; PAS (ácido para-aminosalicílico) = 5 ug/ml y EMB (etambutol) = 4 ug/ml. Las 62 cepas ensayadas (100%) se comportaron sensibles a PAS. De 22 cepas, 11 (50%) fueron resistentes a una sóla droga: INH; 7 (31,8%) a dos drogas; éstas fueron: INH y EMB 4 (18,2%); INH-RIF 2 (9,1%); INH-SM 1 (4,5%) y 4 cepas (18,2%) a tres drogas: INH-RIF-SM 2 (9,1%) y INH-EMB-SM 2 (9,1%). Los porcentajes de cepas de Mycobacterium tuberculosis resistentes a una o más drogas constituyen un importante índice para evaluar los programas de control de tuberculosis de una región. Se concluye, por lo tanto, la necesidad de la aplicación de programas de control eficases para la disminución paulatina de porcentajes de resistencia en nuestro medio