Chapter 14-16 Quiz

Question 1

Describe the 4 types of symbiosis

Answer 1

1. Mutualism - both benefit
2. Commensalism - 1 benefits, other neither benefits or harmed
3. Parasitism - 1 benefits, 1 harmed
4. Ammensalism - 1 harmed, other neither benefits nor harmed

Question 2

Describe resident vs. transient microbiota

Answer 2

Resident microbiota remain a part of the normal microbiota for most of a person’s life.
Transient microbiota remain in the body for only a few hours to a few months.

Question 3

Describe the concept of microbial antagonism

Answer 3

Normal microbiota uses nutrients, take up space, and release toxic byproducts, making it less likely that pathogens can compete well enough to establish and produce disease.

Question 4

List 4 mechanisms by which normal microbiota can become pathogenic (opportunistic pathogens)

Answer 4

1. Immune suppression
2. Changes in normal microbiota (microbial antagonism)
3. Introduction into an unusual site (eg. E. coli in urinary tract)
4. Stressful conditions

Question 5

Three types of reservoirs of infection in humans

Answer 5

1. Zoonoses - animal host to humans
2. Human carriers
3. Non-living reservoir (food, water soil, etc)

Question 6

List 4 portals of entry to the human body for invading pathogens

Answer 6

1. Skin
2. Mucous membranes
3. Placenta
4. Parenteral (under skin)

Question 7

What is the basic definition of disease

Answer 7

Host is harmed; normal functioning is disrupted.

Question 8

Describe the difference between infection and disease

Answer 8

Infection is the invasion of a pathogen. Disease only results if the pathogen multiplies sufficiently to adversely affect the body.

Question 9

Describe the difference between signs and symptoms

Answer 9

Signs are objective; measurable or observable by others.

Symptoms are subjective; only felt by patient.

Question 10

Define a syndrome

Answer 10

A group of signs and symptoms that characterize a condition or disease.

Question 11

State Koch’s Postulates

Answer 11

1. Suspected agent must be present in every case of the disease.
2. Agent must be isolated and grown in pure culture.
3. Cultured agent must cause disease when inoculated into healthy, susceptible host.
4. The same agent must be found in the diseased host.

Question 12

What it the difference between pathogenicity and virulence?

Answer 12

Pathogenicity is the CAPACITY to cause disease.

Virulence is the DEGREE of pathogenicity (i.e., relative ability of a pathogen to cause disease)

Question 13

Define “virulence factors” and list 4.

Answer 13

Virulence factors are any TRAIT that enables a pathogen to cause disease.

1. Adhesion
2. Extracellular enzymes (hyaluronidase, collagenase allow invasion of DEEPER tissues)
3. Toxins (exotoxins, endotoxins)
4. Antiphagocytic factors

Question 14

Examples of exotoxins

Answer 14

Cytotoxins, Neurotoxins, Enterotoxins, Hemolysins, Leukocidins

Question 15

What are the effects when Lipid A is released in the body?

Answer 15

• Triggers release of cytokines
• Activates complement cascade
• Activates coagulation cascade

Question 16

Name the 5 stages of infectious disease

Answer 16

1. Incubation (no signs)
2. Prodromal (mild, general signs/symptoms)
3. Illness (full blown signs/symptoms)
4. Decline
5. Convalescence

Question 17

Three modes of disease transmission

Answer 17

1. Contact transmission
2. Vehicle transmission
3. Vector transmission

Question 18

Three types of contact transmission

Answer 18

1. Direct contact
2. Indirect contact (fomites)
3. Droplet (within 1 meter and close in time)

Question 19

Three types of transmission by vehicles

Answer 19

Waterborne, airborne, foodborne

Question 20

Two types of transmission by vectors

Answer 20

Biological (arthropods)

Mechanical (on insect bodies)

Question 21

What is the term for an infection that is the direct result of a medical procedure

Answer 21

Iatrogenic

Question 22

Exogenous vs. Endogenous infection

Answer 22

Exogenous infections are infections from a source other than the patient.
Endogenous infections are infections from patients’ own microflora.

Question 23

Three types of epidemiological studies

Answer 23

1. Descriptive epidemiology - Collect info during outbreak, attempt to find index case, break chain of transmission
2. Analytical Epidemiology - Usually retrospective, to try determine cause of outbreak (tobacco and lung cancer)
3. Experimental epidemiology - tests a hypothesis about the cause of a disease. Prospective, case controlled experiments

Question 24

Incidence vs. Prevalence

Answer 24

Incidence is the number of new cases.

Prevalence is the number currently infected; cumulative.

Question 25

Endemic vs. Epidemic vs. Pandemic vs. Sporadic

Answer 25

Endemic - occurs at a relatively stable incidence
Sporadic - only a few scattered cases occur
Epidemic - increase in number of cases over historic
Pandemic - epidemic occurs simultaneously on more than one continent

Question 26

Common-source epidemic vs. propagated epidemic

Answer 26

In a common-source epidemic, there is no person to person spread (e.g., food poisoning). The number of incidence tend to spike then diminish quickly.
In a propagated epidemic (e.g., common cold), the number of incidence tend to increase more gradually and take longer to decrease.

Question 27

Describe the first, second, and third lines of defense against pathogens

Answer 27

First line of defense is nonspecific and includes physical barriers, chemical barriers, mucous membranes.
Second line of defense is nonspecific and includes phagocytosis, complement, interferon, inflammation, fever.
Third line of defense is specific and includes lymphocytes, antibodies.

Question 28

Which of the leukocytes is the major phagocytic cell

Answer 28

Neutrophils (a granulocyte)

Question 29

Name the different types of leukocytes

Answer 29

Granulocytes: Neutrophils, Eosinophils, Basophils
Agranulocytes: Lymphocytes, Monocytes, NK cells

Question 30

What is the major role of monocytes

Answer 30

Monocytes leave the blood by diapedesis and mature into MACROPHAGES, which are phagocytic cells of the second line of defense. Include resident and migrating macrophages.

Question 31

Components of the second line of defense

Answer 31

• Phagocytosis
• Extracellular killing by leukocytes
• Specialized receptors recognize invaders. Toll-like receptors and NOD proteins recognize PAMP (pathogen-associated molecular patterns, s/a LPS, peptidoglycan, viral double stranded RNA)
• Nonspecific chemical defenses. Interferons and complement
• Inflammation
• Fever

Question 32

Describe the two major phagocytes

Answer 32

• Neutrophils are the most abundant WBC and are very active phagocytes that eat bacterial and small particles. Migrate quickly.
• Macrophages migrate more slowly and eat cell debris and bacteria.

Question 33

Three ways of avoiding death by phagocytosis

Answer 33

1. Chemotaxis: don’t produce chemoattractants
2. Adherence and ingestion: antiphagocytic capsule or proteins that interfere with adherence
3. Digestion: Escape phagosome, prevent lysosomal fusion, survive inside phagolysosome

Question 34

How to NK cells kill

Answer 34

NK cells are lymphocytes that act mostly non-specifically.
Recognize body cells with reduced MHCI.
Mode of action is extracellular killing via perforin-granzyme pathway. Poke holes in cell membranes and triggers cascade.

Question 35

Which leukocyte attacks parasites

Answer 35

Eosinophils

Question 36

Three major functions of the complement system

Answer 36

• OPSONIZE microbes for phagocytosis
• Enhance INFLAMMATION
• Lyse invading microbes through formation of Membrane Attack Complex (MAC)

Question 37

Three ways to activate complement

Answer 37

• Alternative pathway
• Classical pathway
• Lectin pathway

Question 38

Complement activation is carried out by which enzyme

Answer 38

C3 convertase

Question 39

What are the components of C3 convertase

Answer 39

C3b + Bb