Portal of entry - Generally any orifice that leads to internal organs whether natural or caused. Colonization of mucosal surface or site of injury and multiplication . Maintains a constant, non-transient population. Specific pathogens will have a predilection for a unique tissue. Obligate intracellular pathogens must invade.
Invasion probably is a function of both the infected cell and the bacterial cells.
Target cells may actually engulf the bacterium through an endocytic response. Not all pathogens must invade to exert a pathologic disease. B. Direct spread 1. C. Molecules that confer resistance to host immune and non-immune clearance mechanisms 1. Resistance to phagocytosis 3.