Section 3 Flashcards
What has changed from the 1900’s to now in regards to deaths?
- Decreased deaths from infectious diseases
- Increased deaths from heart disease & cancer
Is the immune system 100% protective?
No, because diseases still exist
What is the difference in the generations times of bacteria and host cells?
Average generation for bacteria is 1 hour, while for host cells it is 20 years
What are 2 characteristics that microbes posses to overcome host defenses?
- Evolution
- Gene exchange on plasmids/transposons
What kind of competition is going on once a pathogen enters a host?
Whether or not the number of microbes can be kept below the threshold level
What does a delayed immune response mean?
Disease and shedding
Why is there a higher prevalence of disease in the winter?
Because people stay inside and are much closer to other people, therefore increasing the chance of coming in contact with an infected individual
What does a pathogen need to do once they enter the body?
Adapt and change
Define disease threshold
The level that a microbe must reach to produce a disease
If someone has a pathogen that is below threshold, can they spread to other people?
Yes, not being in the disease state does not mean that they are not infectious
What is needed for a beneficial host-pathogen relationship?
Adaptation of both pathogen and host without extensive damage
What are the causes of microbial infections that can occur when antimicrobial defences are intact?
- Microbial attachment/penetration
- Biting arthropod
- Skin wound/animal bite
What are the steps of infection?
1) Attachment and possible entry into the body
2) Local or general spread in body
3) Multiplication
4) Evasion of host defences
5) Shedding from body
6) Damage to host
Do pathogens always damage the host?
No, but some damage usually occurs during shedding
Why did Koch create his postulates?
To determine what microorganism caused a certain disease
What are Koch’s postulates?
1) Suspected germ must be present in every case of the disease
2) Must be able to isolate and culture it
3) Must be able to inject pure culture into a healthy individual and cause disease
4) Must be able to isolate suspected germ from newly infected individual
What are some challenges associated with Koch’s postulates?
- Unculturable organisms
- Host immunologic factors
- Involvement of more than one pathogen
- Infections only in humans
What are the new criteria for Koch’s postulates?
1) Suspected germ should be associated with pathogenic strains much more than non-pathogenic strains
2) Inactivation of genes should decrease pathogenicity
3) Replacement of mutated gene should fully restore pathogenicity
4) Gene should be expressed during infection and disease
5) Antibodies against the gene should protect the host
What are factors that influence the severity of an infection?
- Dose and route of infection
- Age
- Sex
- Nutritional status
- Genetic background
What is an example of an uncultarable organism?
Treponema pallidum pallidum
What is an example of a disease caused by host immunologic factors?
Rheumatoid arthritis
What is an example of a pathogen that involves more than one microbe?
HDV
What is an example of a pathogen found only in humans?
HIV
