15.2/17.3 Flashcards
What are Koch’s Postulates?
Set of standards that must be met to demonstrate that X pathogen causes X disease
What is step 1 of Koch’s Postulates
The suspected pathogen must be found in every case of disease and not be found in healthy individuals
What is step 2 of Koch’s postulates?
The suspected pathogen can be isolated and grown in pure culture
What is step 3 of Koch’s postulates?
A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate 1
What is step 4 of Koch’s postulates?
The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2
What are Koch’s wrong assumptions?
- Pathogens are found only in diseased individuals
- All subjects are equally susceptible to infection
- All pathogens can be grown in culture
What does molecular Koch’s Postulates identify instead of pathogen?
gene
What is the first step of Molecular Koch’s Postulates?
The phenotype should be associated only with pathogenic strains of a species
What is the second step of Molecular Koch’s Postulates?
Inactivation of the suspected gene(s) associated with pathogenicity should result in a measurable loss of pathogenicity
What is the third step of Molecular Koch’s Postulates?
Reversion of the inactive gene should restore the disease phenotype
What are the few limitations of Molecular Koch’s Postulates?
- Genetic manipulation of some organisms isn’t possible with current techniques
- Some diseases do not have suitable animal models
Ability of a pathogen to cause disease?
Pathogenicity
Degree of pathogenicity?
Virulence
What is ID50? Related to Morbidity or Mortality?
Median Infectious dose - no. of pathogens required to infect 50% of those inoculated; Morbidity
What is LD50? Related to Morbidity or Mortality?
Median lethal dose - no. of pathogens required to kill 50% of those infected; Mortality
What pathogen can cause disease in a host regardless of the host’s resident microbiota or immune system?
Primary Pathogen
What pathogen can only cause disease in situations that compromise the host’s defenses?
Opportunistic pathogen
What are the 5 stages of Pathogenicity?
- Exposure to host
- Adhesion
- Invasion
- Infection
- Transmission
What are TORCH infections?
Pathogens that can cross placental barrier
What is adhesion in the stages of pathogenicity?
The capability of colonization
What are molecules/structures that bind to certain host receptors called?
Adhesins
What is a production of community glycocalyx called?
Biofilm