1. HOST–MICROBE RELATIONSHIPS AND DISEASE PROCESSES
CHAPTER 14

2. Symbioses – “living together”
Mutualism - both organisms benefit.
Commensalism - 1 organism benefits and the other neither benefits nor is it harmed.

3. Symbioses
Parasitism - one organism (the parasite) benefits and the other (the host) is harmed.
Opportunism – exploit a food source or type of environment.

4. Symbioses

5. Infection and Disease
Contamination - refers to the presence of microorganisms.
Infection - pathogens invade the body.
Disease - pathogens or other factors disturb the state of health such that the body cannot perform its normal functions.
Infestation - refers to the presence of worms or arthropods in or on the body.

6. Pathogenicity Concepts
Pathogenicity - the capacity of a pathogen to produce disease.
Virulence/Avirulence - the intensity of a disease caused by a pathogen.

7. Normal Microflora Populations
Resident - microorganisms found in or on the body that do not normally cause disease.
Transient - those present temporarily and under certain conditions.

8. Koch’s Postulates 1. specific causative agent must be observed
2. The agent must be isolated and grown in pure culture.
3. Hosts must get the same disease when inoculated.
4. The agent must be reisolated and show to be the same causative agent.

9. Satisfying Koch’s Postulates

10. Kinds of Disease Infectious - caused by infectious agents.
Non-infectious - caused by other factors.
Communicable - contagious, infectious disease spread from one host to another.
Non-communicable - infectious disease cannot be spread from host to host and may be acquired from soil, water, or contaminated foods.

11. The big picture on what microbes can and will do!

12. How Microbes Cause Disease
Direct Action
Bacterial Toxins –
Endotoxins - part of the cell wall of Gram-negative bacteria and are released when cells divide or are killed.
Exotoxins - produced by and released from bacteria, 2 TYPES:
Neurotoxins - affect the nervous system.
Enterotoxins - affect the digestive system.

13. How Microbes Cause Disease
Toxoids - inactivated exotoxins that retain antigenic properties and are used for immunization.
Cytopathic Effects (CPE) - damage cells and produce a variety of observable changes via viruses.

14. Virulence Factors

15. Vocabulary Terms Sign - an observable effect of a disease.
Symptom - an effect of a disease felt by the infected person.
Syndrome - a group of signs and symptoms that occur together.
Sequelae – name given to the after effects of disease; bacterial infections causing permanent heart valve damage.

16. Vocabulary Terms
Acute -
Chronic -
Subacute -
Latent -

17. Vocabulary Terms Local infection Focal infection Systemic infection
Septicemia
Bacteremia
Viremia

18. Vocabulary Terms Primary infection Secondary infection Superinfection
Mixed infection
Inapparent (subclinical) infection

19. Infectious Disease Stages
Incubation - time between infection and the appearance of signs and symptoms of a disease.
Prodromal - stage during which pathogens begin to invade tissues; it is marked by early nonspecific symptoms.
Invasive - period during which the individual experiences the typical signs and symptoms of the disease. During this phase the signs and symptoms reach their greatest intensity at the acme.

20. Infectious Disease Stages
Decline - stage daring which host defenses over­come pathogens; signs and symptoms subside during this phase, and secondary infections may occur.
Convalescence - stage during which tissue damage is repaired and the patient regains strength. Recovering individuals may still transmit pathogens to others!

21. Disease Stages and Microbe Populations

23. Control of Infectious Disease
Drugs
Immunization
Sanitization
Future Challenges