Host Pathogen Interactions Flashcards
What is the difference between a principal pathogen, an opportunistic pathogen and commensal organisms?
Principal pathogens: regularly cause disease in only a proportion of susceptible hosts with a normal immune system
Commensals: live on you and in you but don’t cause damage and actually maintain normal physiology
Opportunistic pathogen: don’t normally cause disease unless they have the “opportunity” to so, for example when you’re immune compromised
Koch’s postulates are to establish what?
Whether a specific organism causes disease
What are #Kochs_Postulates?
Koch’s postulates:
- Organism has to be in all cases of diseased folks (but not in healthy folks)
- Bug has to be isolated from the diseased folk and grown in culture
- Disease is reproduced in a new host when bug is inoculated in a susceptible host
- The bug has to be isolated from the newly infected host and cultured (and basically found to be the same one)
What are #Molecular_Koch’s_Postulates?
Factors to determine which specific factor contributes to a bug’s virulence
The 3 molecular Koch’s postulates are ___
- Gene encoding the phenotype should be ass’d with the pathogenic strain (and not in the non pathogenic strains)
- Inactivating the gene results in reduction of virulence
- Restoring the wildtype gene re-establishes virulence
The most common outcome of infection is ___
No #symptoms
Host factors that affect the emergence of new infections include changes in behavior, ___, ___, contamination of environment and food supply and ___
Host factors:
Changes in behavior: e.g. AC can lead to propagation of certain bugs as is the case of Legionella, or new eye infections with contact lenses
Expanding populations and increased travel: potential zoonotic transfer with folk going to new places and increasing travel allows for the easy propagation of these infections
Contamination of environment and food supply
Immunosuppression: one can be susceptible to infection if your immune system is dampened for whatever reason
What are some microbial factors that effect the emergence of new infections?
Short generation time: bacteria reproduce super quickly and new mutations produced with each generation can propagate quickly as well
Acquisition of new genetic material from other bacteria
Changes in vector distribution (like if you have a new vector for a particular bug, that might also affect the emergence of new infections)
The 3 ways bacteria can acquire new genetic material are by ___
Conjugation
Transformation
Transduction
Describe the 3 ways thru which bacteria can acquire new genetic material
Conjugation: exchange of dna between bacteria by direct contact (#bacteria_sex). Can also happen between unrelated bacteria
Transformation: transfer of “naked” dna >> basically one bacteria can release its dna into the cytosol and another bacterium can take that dna up
Transduction: transfer of dna mediated by a bacteriophage
What is the difference between commensals and pathogens if commensals follow the same steps as pathogens do in the infectious cycle?
Commensals do all of the steps in the infectious cycle EXCEPT cause damage (i.e. disease)
Two barriers for bugs to overcome as they try to enter the host are ___
What in the body serves as an ecological barrier to bug infection?
Entry into the host: barriers include the skin and mucosal surfaces
Overcoming barriers: overcoming anatomical barriers like the skin would normally require some kind of trauma to the barrier; ecological barrier = the host microbiome
The first step in establishment is ___
T/F: Bugs that don’t adhere are equally as virulent as those that do
The first step in establishment is adherence
Adherence is usually high avidity and over long distances to overcome electrostatic repulsion between the bug and the host cell surface
Adherence is also the result of adhesins on the surface of the bug, and receptors on the surface of the host cell
Mutants that aren’t adherent are typically avirulent
Describe the role of fimbriae/pili
Fimbriae/pili: rod like things that protrude from the bug’s cell surface. Proteins at the tip of these things actually mediate adherence
**note that the pilus rod provides the distance between the two negatively charged surfaces of the host cell and the bug cell to overcome electrostatic repulsion**
What is the significance of a #biofilm to bug adherence
Staph epidermidis can adhere to catheters via formation of a biofilm
Many bugs form biofilms on foreign surfaces
The biofilms are typically composed of polysaccharides and other things that not only help with adherence but are also resistant to anti-microbial treatment