Virulence Factors Flashcards
What is a pathogen
A microorganism which is able to cause disease is a host organism
Eg.
- opportunistic pathogen: a member of the normal microbiota (is already in your body) only causes disease in an immunocompromised host (if immune system is down)
- Primary pathogen: environmental microbe that is able to cause disease in an healthy individual
What is pathogenicity
The ability of a pathogen to cause disease
E.g
bacterial diseases; ear infections, food poisoning
Viral diseases; AIDS, Covid 19, influenza (flu)
Fungi diseases; Wringworm
Protists diseases; Malaria
What is virulence
The degree or intensity of pathogenicity
(Some are worse than others)
What are the chains of infection
- Agent (the identity eg. Virus)
- Virulence (the intensity of it)
- Dose (how much of that pathogen causes the disease)
- Exposure (how did it get there)
- Susceptibility (does host have any underlying factors e.g are they diabetic)
What are the steps to the Molecular Koch’s postulates
What are the virulence factor mechanisms
. Adhesion > attach themselves to the receptors on the host cell
. Evasion of phagocytosis
. Immunosuppression
. Toxigenicity: exotoxins and endotoxins
What does an adhesion do
It attaches themselves to the receptors on the host cell and forms of it are:
- pilli > can retract and extend allow movement
- fimbriae >
- capsules > helps adhesion and helps in immune evasion prevent phagocytosis. Prevents adhesion of antibodies (weakens the immune system)
- bacterial cell walls (adhesins) > bind to targeted host cell surface, resits physical removal which allows colonisation
What is an exoenzyme
Extracellular enzymes: enzymes secreted by cells which function outside of those cells, invade deeper tissues and enables invasion/support against immune system
E.g. proteases which degrades collagen in connective tissues to promote spread of colonisation
What are toxins
They are poisons produced by pathogens, to cause damage to host cells. The two types are:
- Endotoxins > come from gram-negative bacteria, don’t live on oxygen. When released they stimulate general systemic inflammatory response. Remain stable in high temp.
- Exotoxins > strong protein molecules. Gram negative + positive bacteria. Target specific receptor cells. Low concentrations of exotoxins can be lethal.
What is presence of bacteria in the blood called
Bacteraemia
What is presence of multiplying bacteria in the blood called
Septicaemia
In order to survive, pathogens require a source of nutrients, protection from harmful elements and:
Colonization of a niche in the host
Some enveloped viruses use antigenic variation which makes it difficult for the immune system to recognise different strains of the virus. Which type of antigenic variation results in a major change in spike proteins due to gene reassortment?
Is it Antigenic drift or Antigenic shift
Antigenic shift
Which pathogen type is always a member of the normal microbiota and only causes disease in an immunocompromised host?
Opportunistic pathogen
Which type of pathogen is an environmental microbe that is able to cause disease in an otherwise healthy individual?
a.
Primary pathogen
b.
Opportunistic pathogen
c.
Individual pathogen
d.
Discreet pathogen
Primary pathogen
