Host-Parasite Relationships Objectives Section 19.1 Microorganisms that grow in or on other organisms, imparting no benefit, are parasites. Infection is the process by which a parasite grows in its host. If the parasite causes harm, it is a pathogen. The ability to cause disease is influenced by the complexity of host-parasite interactions.
Pathogens cause disease, but disease is limited by a variety of host defense mechanisms.
Define normal flora in terms of pathogenicity. Distinguish between infection and disease. Section 19.1 Animal bodies are favorable environments for the growth of many microorganisms, including pathogens. The initial colonization by a pathogen is on the surface of the host, often on the mucous membranes. The skin is a dry, acidic environment that is not conducive to the growth of most microorganisms.