One of the important functions of the tubotympanum is to protect the middle ear from invading organisms. The host develops a number of strategies for this function (e.g., mucociliary protection, antibacterial secretory products, immunodefense, and phagocytosis). The bacteria also develop their strategy to evade the host protection by enhancing adherence to the mucosal surfaces, impairing mucociliary function, and evading phagocytosis.