ASPECTS ON THE INTERACTION OF STREPTOCOCCUS-PNEUMONIAE AND HAEMOPHILUS-INFLUENZAE WITH HUMAN RESPIRATORY-TRACT MUCOSA

Haemophilus influenzae and Streptococcus pneumoniae are common causes of respiratory tract infections. H. influenzae attach to receptor epit opes in mucins and in epithelial cell membranes. Attachment is followe d by an epithelial cell cytokine response. Secreted cytokines then ini tiate inflammation, upset the integrity of the mucosal barrier, and le ad to disease. S. pneumoniae do not bind to mucins but attach to respi ratory tract epithelial cells. Attachment is increased by viral infect ion of the epithelial cells. Unlike H. Influenzae, S. pneumoniae induc e apoptosis in epithelial cells, thus disrupting the mucosal barrier. Attachment and persistence is counterbalanced by antiadhesive as well as bactericidal molecules in secretions such as human milk. These exam ples illustrate the balance between host defenses and microbial virule nce as it has coevolved to maintain the health of the respiratory muco sa.