infectious diseases

What is the innate immune response's level of protection?

Not 100% protective

How do microbes evade host defenses?

By possessing numerous characteristics

How does the generation time of bacteria compare to that of the host?

Bacteria have a much shorter generation time, evolve faster

What is gene exchange in microbes associated with?


Antibiotic resistance and virulence gene

what is the relationship between host acquired IR and microbial activity

microbes can multiply and spread faster

what happens during a delayed IR

leads to disease and shedding

what is the adaptation and balanced pathogenicity in host-pathogen relationships

• Adaptation occurs over time

• Less damage with longer relationships

• Example: Myxoma virus in rabbits

  • Initially lethal, but less lethal strains evolved

What are the steps of infection?

1. Attachment and entry into the body

2. Local or general spread

3. Multiplication

4. Evasion of host defenses

5. Shedding from the body

6. Damage to host (not always required)

What are Koch’s Postulates used for?

To define organisms causing infection

What are koch’s postulate

1. suspected germ must be present in every case of the disease

2. the germ must be isolated and grown in pure culture

3. the cultured germ must cause the disease when it is inoculated into healthy animal

4. the same germ must be reisolated from the diseased experimental host. 

What are the challenges associated with Koch’s Postulates?

• Unculturable organisms (e.g., Treponema pallidum)

• Host immunologic factors (e.g., rheumatoid arthritis)

• Involvement of multiple pathogens (e.g., HDV)

• Infections only in humans (e.g., HIV)

what is the role of hepatitis D virus in liver cancer

causes cancer only with hepatitis B co-infection

what are the molecular evolution aspects of Koch’s postulate

1. Virulence trait association with pathogenic strains

2. Inactivation decreases pathogenicity

3. Replacement restores pathogenicity

4. Gene expression during infection

5. Immune protection against gene products

what factors influence the severity of an infection

• dosage

• age

• route

• sex

• nutrition

• genetics

what does the biological response gradient illustrate

• Severity of infection varies

• Influenced by multiple factors

• Asymptomatic individuals exist

• Infection rates exceed disease rates

who is more prone to disease according to the biological response gradient

seniors and children

What is the relationship between the number of pathogens and GI tract bypass?

A large number is needed to bypass

What varies in the establishment of infection?

Features of both host and pathogen