Early Stages of Infection After Pathogen Entry

In this chapter, we describe the early stages of the pathogenic cycle involving entry into the host. For example, some bacteria may enter into epithelial cells, proliferate and then spread at the epithelial surface before being transmitted to another host. Some pathogens then migrate past the epithelial layer to deeper tissues causing invasive infections. Examples of some of the major bacterial, viral and fungal pathogens affecting the epithelial surfaces in the body are provided. The body produces a strong inflammatory immune response to pathogens at the epithelial surface. An introduction to the components of the inflammatory response including the phagocytic cells and the lymphatic system is provided. In addition, the nutritional requirements for invading bacteria including the importance of iron is discussed.