Immunity to Bacterial Pathogens

Question 1

What is the human microbiome?

Answer 1

All the microbes that call us home
Very few microbes are pathogens

Question 2

What is a pathogen?

Answer 2

Microbes that can cause disease

Question 3

What is an infection?

Answer 3

When a microbe replicates in or on a host

Question 4

What is disease?

Answer 4

When microbial infection damages the host

Question 5

What is pathogenicity?

Answer 5

The ability of an organism to cause disease
Qualitative trait

Question 6

What is virulence?

Answer 6

The extent to which a microbe can cause disease

Question 7

What are virulence factors?

Answer 7

The adaptations and traits that promote virulence in a pathogen

Question 8

What is a good pathogen?

Answer 8

One that makes us just sick enough so that it can find a new host

Question 9

What is a bad pathogen?

Answer 9

One that kills us before it has the chance to find a new host

Question 10

What is an opportunistic pathogen?

Answer 10

One that takes advantage of weakened immune systems (immunodeficiency) and causes a disruption in the balance of normal microbes

Question 11

What is an obligate pathogen?

Answer 11

The pathogen must cause disease to be transmitted

Question 12

What is a facultative pathogen?

Answer 12

The pathogen can cause disease but does not require a host to complete its life cycle

Question 13

What contributes to the final outcome of the disease?

Answer 13

Interactions between the host and the microbe

Question 14

What is the relationship between the host and the microbe influenced by?

Answer 14

Virulence of the microbe
The defense mechanisms of the host

Question 15

What are the steps to the establishment of infection?

Answer 15

Pathogen encounter
Host entry
Adhesion and invasion
Immune system evasion
Host damage

Question 16

What is the gram stain of S. epidermidis and what type of pathogen is it?

Answer 16

Gram-positive
Opportunistic bacteria

Question 17

What is the typical role of S. epidermidis?

Answer 17

It is a normal part of the skin microbiome and important in protecting the skin from unwanted pathogens

Question 18

How are we exposed to S. epidermidis?

Answer 18

It is very hardy as it is an ubiquitous component of the human skin

Question 19

How does S. epidermidis enter the host?

Answer 19

Typically nosocomial (hospital borne) through catheters, pacemakers, and plastic implants as a biofilm

Question 20

How does S. epidermidis adhere and invade?

Answer 20

Tolerates changing osmolarity
Adheres via hydrophobic associations
Teichoic acid polymers associate with plastic
Bacterial components bind ECM component of the host (collagen in particular)

Question 21

How does S. epidermidis evade the immune system?

Answer 21

Biofilms provide resistance to antibiotics and protections from AMPs
AMP resistance through efflux pumps
Extensive antibiotic resistant genes
PGA - poly-gamma-glutamic acid production in capsule-like exopolymer

Question 22

What does PGA do?

Answer 22

Protect against phagocytosis and AMPs

Question 23

How does S. epidermidis damage the host?

Answer 23

Through PSM’s (phenyl-soluble modulins) which allows access to host cells

Question 24

What did Pasteur show?

Answer 24

That cells arise from preexisting cells

Question 25

What was the bubonic plague’s causative agent and its route of entry?

Answer 25

Y. pestis and through flea bites

Question 26

How does Y. pestis cause infection?

Answer 26

It replicates in the macrophages and the macrophages then migrate to the lymph nodes
Buboe’s form which is the next route of exposure

Question 27

What did Koch show?

Answer 27

A cause and effect relationship between pathogen and disease

Question 28

What were Koch’s postulates?

Answer 28

1. Pathogen must be present in all cases of disease
2. Must be grown in pure culture
3. Must cause disease from the culture
4. Must be able to reisolate the pathogen in that same form