Colonization Capability of Lactobacilli and Pathogens in the Respiratory Tract of Mice: Microbiological, Cytological, Structural, and Ultrastructural Studies

Respiratory tract infections are among the bacterial infections that affect humans with higher frequency. Those produced by
Streptococcus pneumoniae
are reported to have the highest incidence in the world, affecting both children and old people. As a 2001 report from the World Health Organization (
1
) expressed it, the basic fight of children under 5 yr old is to survive. Five different conditions (acute respiratory infections, diarrhea, measles, palludism, and undernutrition) directly produce more than 50% of the deaths in this age group. Respiratory tract infections in the developing countries in the Americas are among the first three causes of death in children under 1 yr and between the first and second cause in children between 1 and 4 yr old. Pneumonia is responsible for 85 and 90% of deaths in children under 5 yr old (approx 150,000 annually), 95% of them occurring in the developing countries in the Americas.