1. Microorganisms and Disease
How does the human body and various microorganisms interact in terms of disease?

2. Infectious Disease bacteria can produce capsules, enzymes, and toxins
infectious disease is the primary cause of death world-wide
: influenza pandemic killed more than 20 million people world-wide and 500,000 people in the United States

3. Readings question #1:
Describe the “chain of infection”.

4. Infection vs. Disease
Infection: “the entry, establishment and multiplication of pathogenic organisms within a host”
Disease: an abnormal state in which part or all of the body is not properly adjusted or is incapable of performing normal functions; any change from a state of health

5. Factors that Influence the Occurrence of Disease
1) virulence of the organisms
2) portal of entry of the pathogen
3) number of organisms present
4) the resistance of the host

6. Virulence of Organisms
virulence: “relative power of an organism to produce disease”
contamination: “the act of introducing disease germs or infectious material into an area or substance”

7. Virulence (cont’d)
pathogenicity: “the state of producing or being able to produce pathological changes and disease”

8. Types of Infections and Diseases
acute diseases: symptoms develop rapidly but may only last for a short period of time
chronic diseases: develop slowly and are likely to continue for long periods of time

9. Factors Influencing Virulence
Capsules and Endospores

10. Sources of Infection Human Reservoirs: Animal Reservoirs:
Environmental Reservoirs:

11. Portal of Entry 5 portals of entry: 1) skin and mucous membranes
2) respiratory tract
3) digestive tract
4) genito-urinary tract
5) placenta

12. Resistance of the Host mechanical defenses physiological defenses
chemical defenses

13. Mechanical Defenses
Skin: epithelium (epidermis), sebaceous glands, dryness, “necrobiosis”
Eyes: lacrimal apparatus
Saliva: cleansing action
Respiratory Tract: mucus, ciliated epithelium
Urinary Tract: flushing action

14. Physiological Defenses
Inflammation: pus
Fever: degrees
Phagocytosis: phagocyte ingests material

15. Chemical Defenses
Lysozome: enzyme that breaks down cell walls of bacteria
Sebum: sebaceous glands, oily substance, protective film, lowers skin pH
Gastric Juice: HCl, enzymes, mucus, acidic

16. Antigens
“a foreign substance that stimulates the formation of antibodies that react specifically with it”
substance that provoke a specific response
Antibodies: “glycoprotein substance developed by the body in response to, and interacting specifically, with an antigen. Also known as immunoglobulin.”

17. Antigen-Antibody Reactions
1) destroy pathogens by neutralizing the toxins the pathogen produces
2) coat the pathogen with a substance that attracts phagocytes by forming a substance that clumps the antigens together
3) prevent the pathogen from adhering to the body’s cells

18. Types of Immunity Natural (Innate)
Acquired: Naturally Acquired – active, passive
Artificially Acquired
- active: vaccines passive: antibodies
immune serums