mechanisms of bacterial virulence Flashcards
what is a pathogen
an organism that causes disease
what is pathogenicity
capacity to initiate disease
what is virulence
capacity to cause disease and severity of the disease
what is transmissibility
ability to transmit from human-to-human to reservoir-to-human
what is survival infectivity
ability to breach host defences
what are Koch’s postulates
- Microorganism must be found in diseased but not healthy individuals
- Microorganism must be cultured from the disease individual
- Inoculation of a healthy individual with cultured microorganism must cause the same disease
- Microorganism must be re-isolated from the inoculated, disease individual and matched to original microorganism.
what are the steps to infection
transmission adherence invasion survival in host tissue damage
what secretory systems have the capacity to transfer proteins directly from the cytoplasm
T1SS, T3SS, T6SS and T7SS
what secretory systems can only secrete proteins from the periplasm to the outside environment
T2SS, T5SS T8SS T9SS
what are the routes of entry for pathogens
respiratory, gastrointestinal, urinary tract, mucus membranes and skin
what is adhesion
process by which organisms attach themselves to our cells
how is initial attachment of bacteria to cells mediated?
fibrae/pilli and flagella
what are EPS?
expolysacchardies they can further mediate attachment of pathogen to cells.
they are hydrophobic structures that displace water promoting closer contact between cells
what is invasion
crossing host barriers, extra-cellular environments are harsh environments.
what are the two things bacteria produce to induce entry into target cells
zipper and trigger
what is zipper
expression of adhesion proteins that bind with high affinity to host receptors.
binding tricks the cell that another one is close by inducing membrane arrangements
bacteria is engulfed
what is trigger
bacterial effector proteins are injected directly into the cytoplasm using T3SS.
activates signalling pathways = cytoskeleton rearrangements
example of zipper
listeria
example of trigger
salmonella and Shiga
how do bacteria survive in the host?
- some escape into the cell cytoplasm rapidly multiplying and escaping to adjacent cells & repeating
- cytosol is a neutral pH, must have specific adaptations to import metabolic by-products from the cytoplasm
- bacteria need to hide from host immune responses such as autophagy.
- avoid lysosomal killing y interfering with endoscope maturation pathway
what is the obligate survival?
pathogens require a host to fulfil their life cycle
what is facultative survival?
pathogen can live in multiple different conditions
what is extracellular survival
pathogens that thrive independent of a host cell
example of what pathogens thrive independent of a host cell
E.Coli
