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HOST–MICROBE RELATIONSHIPS AND DISEASE PROCESSES

CHAPTER 14

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Symbioses – “living together” Mutualism - both organisms

benefit. Commensalism - 1 organism

benefits and the other neither benefits nor is it harmed.

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Symbioses Parasitism - one

organism (the parasite) benefits and the other (the host) is harmed.

Opportunism – exploit a food source or type of environment.

Symbioses

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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.

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Pathogenicity Concepts

Pathogenicity - the capacity of a pathogen to produce disease.

Virulence/Avirulence - the intensity of a disease caused by a pathogen.

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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.

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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.

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Satisfying Koch’s Postulates

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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.

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The big picture on what microbes can and will do!

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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:

1.Neurotoxins - affect the nervous system.2.Enterotoxins - affect the digestive

system.

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.

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Virulence Factors

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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.

Vocabulary Terms

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Acute -

Chronic -

Subacute -

Latent -

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Vocabulary Terms Local infection

Focal infection

Systemic infection

Septicemia

Bacteremia

Viremia

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Vocabulary Terms Primary

infection

Secondary infection

Superinfection

Mixed infection

Inapparent (subclinical) infection

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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.

Infectious Disease Stages Decline - stage daring which host

defenses over come 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!

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Disease Stages and Microbe Populations

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Control of Infectious Disease Drugs

Immunization

Sanitization

Future Challenges