Bacterial Pathogenesis

Numerous physical and chemical attributes of the ho st protect against bacterial infection. These defenses include the antibacterial factors in secretions covering mucosal surfaces and rapid rate of replacement of skin and mucosal e pith lial cells. Once the surface of the body is penetrated, bacteria encounter an environme nt virtually devoid of free iron needed for growth, which requires many of them to s cavenge for this essential element. Bacteria invading tissues encounter phagocytic cell s that recognize them as foreign, and through a complex signaling mechanism involving int erleukins, eicosanoids, and complement, mediate an inflammatory response in whi ch many lymphoid cells participate.