MICR 2123 Lecture Notes - Lecture 18: Virulence Factor, Median Lethal Dose, Vertically Transmitted Infection
18 Nov 2016
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Document Summary
Mammals have elaborate physical, chemical, and immunological defenses that protect against disease-causing microbes, or pathogens (chapters 23 and 24), yet every fortress has its weakness. Pathogenic microbes exploit those weaknesses, and the result is disease. Here in chapter 25, we explore the strategies that different bacterial and viral pathogens use to accomplish this feat. The term parasites, includes bacteria, viruses, fungi, protozoa, and worms that colonize and hard their hosts. In practice, however, only disease-causing protozoa and worms are called parasites, whereas bacterial, viral, and fungal agents of disease are referred to as pathogens. Organisms that live on the surface of a host are called ectoparasites. Primary pathogens cause disease in healthy hosts. Opportunistic pathogens cause disease only in immunocompromised patients (lower immunity. The term pathogenicity refers to an organism"s ability to cause disease. It is defined in terms of how easily an organism causes disease (infectivity) and how severe that disease is (virulence)
