Mechanisms of Pathogenesis

Question 1

Candida Auris and hospitals

Answer 1

Fungus that only causes infection in hospitals

Question 2

Pathogen

Answer 2

disease-causing agent

Question 3

What type of organisms can be pathogens

Answer 3

fungi, virus, bacteria, protists, prions

Question 4

Pathogenicity vs. virulence

Answer 4

Pathogenicity: ability to cause disease (highly pathogenic = able to cause disease easily)
Virulence: Severity of disease (degree of pathology) - how bad is the pathogen

Question 5

Pathogenicity and virulence of the common cold, Rhinovirus

Answer 5

Pathogenicity = high
Virulence = low

Question 6

Pathogenicity and virulence of Ebola virus

Answer 6

Pathogenicity = high
Virulence = High

Question 7

How do we classify pathogens?

Answer 7

Primary pathogen: capable of causing disease in healthy hosts (Rhinovirus)

Opportunisitc pathogens: cause disease in immunocompromised host

Question 8

What must a pathogen be able to do to be classified as a primary pathogen

Answer 8

must have means to breach immune system defenses (since it affects healthy hosts)
* e.g. Mycobacterium tuberculosis - replicates and destroys macrophages

Question 9

What causes a person to be immunocompromised

Answer 9

• Presence of other diseases (HIV/AIDS)
• Genetic defects in immunity
• Autoimmune disorders
• Induction by drugs (e.g. for organ transplant - take immunosupressants)
• Extremes in age
• Lack of proper nutrition

Question 10

Most fungal pathogens of humans are

Answer 10

opportunistic (Candida)
* many human deaths from fungal diseases occur in AIDS patients

Question 11

Your friend at the CDC tells you about a new disease-causing bacterium identified. Healthy people are easily getting the disease, and the bacterium has clear adaptations to infect human cells. Not much damaged is caused by the disease however. How would you classify this type of pathogen

Answer 11

Primary pathogen with high pathogenicity and low virulence

Question 12

Seven elements/mechanisms of pathogenesis

Answer 12

1. Maintain a reservoir
2. Transport to host
3. Invade and colonize host
4. Evade host defenses
5. Multiply in host
6. Damage host
7. Leave host

Question 13

Reservoir

Answer 13

animal or place where a pathogen can be found before or after an infection
* source of infection
* may be necessary for pathogen survival

Question 14

Example of the reservoir and vector for Yersinia Pestis (cause of the plague)

Answer 14

• Rats
• Fleas

Question 15

significance of smallpox virus and reservoirs

Answer 15

Lacks a reservoir other than humans
* Why eradication was possible

Question 16

What makes it very difficult to fully eradicate a virus

Answer 16

whether or not it has a reservoir

Question 17

Common modes of transport for pathogens

Answer 17

1. Via other animals - can be a vector or a zoonotic diseases
2. Sexual transmission
3. Drinking contaminated water (water-born pathogens) - fecal-oral route
   * e.g. Vibrio cholerae
4. Air-borne pathogens (Rhinovirus)

Question 18

What pathogen causes the sexuallly-transmitted disease Syphilis

Answer 18

Treponema pallidum

Question 19

Rarer form of pathogen transmission

Answer 19

Would-related pathogens

Question 20

examples of wound-related pathogen

Answer 20

• Clostridium tetani - causes tetanus
• Staphylococcus areus - causes impetigo

Question 21

Main mechanism of a pathogen to invade and colonize a host

Answer 21

Attachment: adhesins are microbial factors that promote attachment to a host surface

Question 22

Mechanisms of evading a host

Answer 22

1. Don’t be recognized
2. Resist phagocytosis
3. Survive (persist) in phagocytic cells/organelles
4. Destroy antibodies

Question 23

What pathogen is known for being good at evading the host by not being recognized

Answer 23

Borrelia burgdorferi - parasite that causes of Lyme Disease
* Decreases surface proteins recognized by host
* Reside in biofilm

Question 24

How can pathogens resist phagocytosis

Answer 24

Capsule (polysaccharide layer) prevent phagocytosis

Question 25

two examples of pathogens that can survive inside phagocytic cells/organelles

Answer 25

• Rickettsia spp.
• Mycobacterium tuberculosis

Question 26

How does the pathogen Niesseria gonorrhoeae avoid antibodies

Answer 26

ImmunoglobulinA (IgA) proteases break down IgA in host

Question 27

Where do pathogens multiply in the host

Answer 27

find the place in the body where they grow the best
* salmonella typhimurium = the intensines
* mycobacterium leprae = nerve cells in the appendages

Question 28

How is a host damaged during pathogenesis

Answer 28

• trigger exaggerated immune response
• Toxins

Question 29

example of an exaggerated immune response with mycobacterium tuberculosis

Answer 29

granulomas - many immue cells aggreate to “wall of infections”
* pathogen get a free hide out within to grow and mutliply

Question 30

Exotoxins

Answer 30

soluble proteins released outside the cell

Question 31

Clostridium tetani

Answer 31

• anaerobic soil Firmicute bacteria
• Causes “lockjaw”

Question 32

What does Clostridium tetani release that causes lockjaw

Answer 32

Secretes an exotoxin (neurotoxin): tetanospasmin
* causes muscle spasms, can tear muscle fiber
* Lethal dose of tetanospasmin for adult = 175 ng

Question 33

Endotoxins

Answer 33

released only when cell lyses eliciting immune response
* usually outer membrane lipopolysaccharides

Question 34

Exotoxins:
a) are secreted by gram-positive bacteria only
b) primarily contain glycolipids
c) are protein toxins made by gram-positive and gram-negative bacteria
d) serve as adhesins for muscosal pathogens
e) contain lipid A

Answer 34

are protein toxins made by gram-positive and gram-negative bacteria

Question 35

mechanisms of leaving the host

Answer 35

• sexual contact
• vertical transmission (parent to offspring)
• Feces (Fecal-oral route)
• Coughing
• Vector-borne