Pathology - Pathogenesis Flashcards
Infection
Any microbial growth not usually present in the host.
Disease
Damage or injury that impairs host function.
Why does the host have different levels of susceptibility and resistance to each pathogen variety?
Has the determinants of pathogenicity are different to each pathogen.
Oppurtunisitc Pathogens
Pathogens usually harmless in healthy people, but virulent in immunocompromised hosts.
How might normal flora cause disease to host.
If the host is immunocompromised
What is pathogenicity measured by?
Pathogen virulence
Virulence
The relative ability of a pathogen to cause disease
How does virulence differ from pathogenicity
Virulence derives from host-pathogen interactions and is influenced by the host, pathogen and the envrionment.
Lethal Dose 50
Describes number of pathogens it takes to kill 50% of animals in a test group.
How is virulence measured?
LD50
Why is it hard to determine LD50 of highly virulent pathogens?
Because highly virulent pathogens show little difference in pathogens it takes to kill 50% compared to 100%.
Double Knock Out
Where two genes are knocked out simultaneously in an organism.
Attenuation
Decreased or complete loss of virulence of a pathogen
What might cause attenuation?
Weakly virulent pathognes in a culture have no selective advantage.
Vectors
A living organism transmitting an infectious agent from an infected animal to a human or other animal.
How might one deliver a heterogenous antigen to bacteria?
Vectors.
How is attenuation artificially achieved?
Employment of recombinant DNA generating live-attenuated bacterial vaccine vectors through deletion of genes involved in virluence.
What is an example of artifical attenuation?
Decreased phoP/phoQ system in salmonella.
Glycocalyx
A polymer secreted by bcateria and coating its surface.
Examples of bacterias adherence capabilities?
Glycocalyx, Fimbraie, Pili and Flagella, capsule and slime layer.
Difference between slime layer and capsule?
S-layer are composed of polymers extending from the cell and capsule surround the cell, important in adhesion in most bacteria.
Where are capsules most commonly employed?
Protecting pathogens against host defense.
What is an example of utilising capsule in host infection?
Steptococcus Pneumonia virulence factor is the capsule.
What does the S.Pneumonia capsule allow it to do?
Grow to vast numbers in host tissues with ability to initate host responses leading infection.
Why might a capsule be essential in infeciton?
Nonencapsulated strains are often phagocytosed very easily.
Where do pili bind specifically?
Host surface glycoproteins.
How are Fimbraie used in E.Coli?
Causing Diarrhoea by enterotoxic strains containg genes for fimbriae colonization factor antigens adhering small intestine where E.Coli grow, causing diarrhea.
EnteroToxin
A toxin produced that affects the intestine.
Why is adherence important?
Provides nutrional acquistional capabilites and protection against envrionmental stress.
What is the first stage in infection?
Invasion
Invasion
The pathogens ability to enter host cells, spread and cause disease.
Where does invasion often occur?
Skin/tissue damage or mucous rich regions.
What do pathogens often do upon entry into a host?
Remain local where multireplicaiton and invasion occurs at a singularity.
Baceremia
Viable bacteria in the blood.
Septicemia
Life threatening reactions to infections.
What is an important note in regards to infection?
It does not always cause host damage.
What is infection dependent on?
Sufficient nutrients for the bacteria and adherence to surfaces.
What is a major limiting growth factor for bacteria?
Iron.
In regards to iron, how does a host respond to bacteria?
Transferrins and Lactoferrins are high affinity iron binders, sequestering it from the host.
How can bacteria counter host iron sequesteration?
Siderophoresn.
What is infection often associated with?
Biofilm formation.
What is an example of biofilm formation in infection?
Dental plaques in tooth enamel by streptococci.
