lecture 2 - microbial virulence Flashcards
What is pathogenicity?
The ability of a microbe to cause infection
What is virulence?
The measure of pathogenicity in a susceptible host
What is a virulence factor?
A gene product that enables colonisation of a susceptible host
What are the 2 microbe and host factors needed for an infection?
virulent microbe + susceptible host = infection
What is the name for lower virulence pathogens that require a susceptible host?
Opportunisitic pathogens
What is the name for higher virulence pathogens that do not require a susceptible host?
obligate pathogens
Where are opportunisitc pathogens found when not infectious?
The microbiome
What factors influence host susceptibility?
age, comorbidities, lifestyle, genetics, immunisation, medication, trauma , etc.
What is microbe-mediated pathogenesis?
microbial virulence factors that directly damage host cells
What is host-mediated pathogenesis?
prolonged/delayed immune responses and/or inappropriate inflammatory response that cause damage to the host itself
What are the characteristics of a gram positive cell wall?
Thick layer of peptidoglycan, with lipoteichoic and teichoic acids.
What are the characteristics of a gram negative cell wall?
Thin peptidoglycan cell wall, with an outer membrane of lipopolysaccharide.
What colour are gram-positive bacteria stained?
Purple
What colour are gram-negative bacteria stained?
pink
What is the function of biofilms & capsules in micobes?
protection from immunes cells, e.g. phagocytes, and allow for adhesion in tissues.
What virulence factor allows for motility?
flagella
What are examples of microbial adhesins?
lipopolysaccharide, pilli, fimbriae, capsule
What are microbial invasins?
Enzymes that act to break down barriers in host tissues
What is drift, in terms of antigenic variation?
variation that leads to seasonal epidemics
What is shift, in terms of antigenic variation?
extreme variation that leads to pandemics
What is the function of mobile genetic elements (MGE)?
Allows bacteria to take up the virulent genes from other bacteria so they can adapt.
