Host-Microbe Interactions (complete)

Question 1

What is an infection?

Answer 1

• When a microbe enters into a relationship w/ the host
• May or may not cause disease

OW OW!

Question 2

What is an infectious disease?

Answer 2

• Disease caused by an infection w/ a microbe
• Some are communicable (transferred from person to person)
• Others are not communicable

Question 3

What does pathogenicity mean?

Answer 3

Capacity of a microbe to damage a host

Question 4

What does virulence mean?

Answer 4

Relative capacity of microbe to damage a host

Question 5

Explain how a microbe is shown to be the cause of a specific disease

Answer 5

Koch’s Postulates:

• Specific microbes present regularly in characteristic lesions of the disease
• Specific microbes can be isolated and grown in vitro
• Injection of cultured microbes into animals reproduces the disease in humans
• Specific microbes can be re-isolated from lesions of the disease in animals

However this may not be possible to do with each disease

Question 6

What are the typical stages in pathogenesis of an infectious disease?

Answer 6

1) Encounter
2) Entry
3) Spread
4) Multiplication
5) Damage
6) Outcome

Question 7

Describe the encounter phase of pathogenesis.

Answer 7

THINK: how the agent meets host

• Contracted endogenously or exogenously?
• Route of infection
• Infectious dose

Question 8

Describe the entry phase of pathogenesis.

Answer 8

THINK: how the agent enters host

• Colonization of body surfaces (contributes to extent/stability of colonization)
• Adherance (mediated by specific binding of pili or non-pili to receptors on host tissues)

Question 9

Describe the spread phase of pathogenesis.

Answer 9

Microbial products can inhibit or promote spread

• Hyaluronidase, elastase, collagenase (spreading factors)
• Coagulase (inhibits )

Types of spread:

1) respiratory/salivary
2) fecal-oral
3) STI
4) Zoonoses (bug vector, vertebrate, bug–> vertebrate)

Question 10

Describe the multiplication phase of pathogenesis.

Answer 10

THINK: how it multiplies in host

Replicating rates in hosts must exceed their clearance by defense mechanisms — clearance done by innate/adaptive immunity

Question 11

Describe the damage phase of pathogenesis.

Answer 11

• Some microbial products causes direct damage
• Some contribute to host damage by blocking/interfering w/ host defense mechanisms
• Most that cause direct damage are surface components, products secreted into medium,

* CLARIFY THIS LAST ONE*

Question 12

Describe the outcome phase of pathogenesis.

Answer 12

Overall what is the outcome after all is said and done

Doesn’t include much of a description

Question 13

Describe the composition and importance of the microbiome in the body

Answer 13

Composed of bacteria in skin, oropharynx, large intestine, vagina

Factors that affect microbiome:

1) Diet
2) Antibiotics
3) Anatomic abnormalities
4) Genetic differences

Important aspects:

1) Effects on tissue/organ differentiation
2) Vitamin production by gut flora
3) Biochemical conversions
4) Competition with pathogens for colonization of body surfaces

Question 14

Compare several disease paradigms that illustrate selected mechanisms of pathogenesis

Answer 14

1) Toxin mediated: cholera
2) Acute inflammation caused by invasive extracellular bacteria: pneumonia
3) Infection by facultative intracellular bacterium: TB
4) Pathology mediated by immune response: Rheumatic fever

Question 15

What is the incubation period?

Answer 15

The lag between exposure and development of clinical symptoms

Sometimes you are contagious during the incubation period, sometimes not — varies in diseases