Virulence Factors Flashcards
Pathogen examples
Bacteria
Virus
Fungi
Protozoa
What is a pathogen
Any microorganism that is able to cause disease in a host organism.
Primary pathogen
Environmental microbe that is able to cause disease in an otherwise healthy individual.
Opportunistic pathogens
Member of the normal microbiota and only causes disease to an immunocompromised host.
Pathogenicity
The ability of the pathogen to cause disease.
What pathogenic diseases do bacteria form
Ear infections
Pneumonia
Food poisoning
Dental caries
Gingivitis/peridontitis
What pathogenic diseases do viruses form
Common cold
Influenza
AIDS
What pathogenic diseases do protists form
Malaria
What pathogenic diseases do funghi form
Athletes foot
Ringworm
Virulence
Degree or intensity of pathogenicity
Virulence factors
Mechanisms that determine the degree to which the pathogen causes damage, invasion and infectivity.
What is the chain of infection
Agent
Virulence
Dose
Exposure
Susceptibility
What is the aim of molecular Koch’s postulates
Identify encoded genes of microorganisms virulence factors.
Process of molecular Koch’s postulates
- Identify microorganism causing disease.
- Extract and grow microorganism in pure culture.
- Introduce microorganism to healthy host.
- This causes disease.
- Microorganism is then extracted again from the now diseased model.
- Microorganism should be identical as original microorganism.
What do virulence factors allow a pathogen to do
Outcompete host cells and resist their defences.
What do microorganisms require to survive;
A suitable environment
Source of nutrients
Protection from harmful elements (establish within the body)
Virulence factor mechanisms
Adhesion
Evasion of phagocytosis
Immunoevasion
Immunosuppression
Toxigenicity (exotoxins, endotoxins)
Enzymatic (exoenzymes)
How does adhesion happen?
Contains surface proteins/glycoproteins called adhesins.
Bins to targeted receptor molecules on host cell surfaces.
Bacteria adhere, resist physical removal and allow colonisation.
Can use one or more adhesin to colonise host cell.
What type of pathogen causes dental caries and what is its adhesin?
Streptococcus mutants.
Adhesin P1.
Examples of adhesion
Pili
Fimbriae
Capsules
Bacterial cell walls
How do capsules aid in adhesion
Some bacteria produce capsules to prevent adhesion of antibodies causing them to breakdown and deterring phagocytosis.
What is the function of Fimbriae?
Contains mycolic acid that alters surface of bacterium to prevent phagocytosis.
What is mycolic acid
Produced in its cell wall and acts as protective coat which deters killing mechanisms when phagocytosed.
What is an exoenzyme
- Extracellular enzyme; secreted by the cell and functions outside the cell.
- Invade host cells within deeper tissues.
- Specific to particular tissues.
- Enables invasion, supports own growth and defends against immune system.
How are exoenzymes virulence factors?
Break down of cells structure allowing pathogen to invade.
Examples of exoenzymes
Proteases - degrades collagen in connective tissue to promote spread
Nucleases
Phospholipases