Infectious Agents

Learning Objectives

1. Explain the major differences between prokaryotic and eukaryotic cells
2. List major types of infectious agents and be able to distinguish between living and non-living
3. Explain key differences among bacteria, fungi, protozoa, and prions
4. Describe how bacteria and viruses reproduce
5. List and describe the four general patterns of viral infection
6. Define 'prion' and discuss the role of prions in the epidemic of bovine spongiform encephalopathy (BSE) in the UK
7. Discuss the role of prions in Creutzfeldt-Jakob Disease (CJD)
8. Discuss how the British BSE epidemic in cattle caused disease in humans

The 5 Kingdoms

Every species can be categorized as a plant, animal, bacteria, fungi, or protozoa. While natural selection implies competition among and within species there is a strong interdependence among species. For example, most bacteria are non-pathogenic and live in and outside our bodies and provide many benefits, such as preventing pathogenic species from gaining a foothold.

Bacteria

With the help of fungi, bacteria play a vital role in breaking down dead organisms.

Healthy internal tissues are free of microorganisms but skin & mucus membranes in our gastrointestinal tract, respiratory tract, and genito-urinary tract are in contact with organisms in the environment and become colonized with many bacterial species. These bacteria are referred to as "normal flora". The normal flora for a human consists of more than 200 species of bacteria, which depend on a variety of factors.

The above chart shows several common bacterium and where they are commonly found on the human body.