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 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
What are toxins and what do they do
Biological poisons produced by some pathogens.
Invade and damage tissue cells.
Toxigenicity
Ability of a pathogen to produce toxins to cause damage to host cells.
(More toxic, more damage)
2 types of toxins
Endotoxins
Exotoxins
What bacteria are endotoxins derived from
Gram negative bacteria
What do endotoxins stimulate
General systemic inflammatory response
What happens if endotoxin concentration is low?
Hosts inflammatory response against infection is effective.
What happens if endotoxin concentration is high?
Causes severe drop in blood pressure, multi organ failure and possibly death.
What is an exotoxins
Potent protein molecule
What types of bacteria are exotoxins?
Mainly gram positive bacteria but some gram negative.
What do exotoxins target and what do they do?
Target specific receptors on specific cells.
Damage cells through individual molecular mechanisms.
3 categories of exotoxins
Intracellular targeting
Membrane disrupting
Superantigens
Presence of bacteria in the blood
Bacteraemia
Pus forming bacteria in the blood
Pyaemia
Presence of toxins in the blood
Toxaemia
Multiplying bacteria in the blood
Septicaemia
Antigenic variations
Surface proteins alter to avoid recognition by hosts immune response
What does the product of exoenzyme coagulase do?
Triggers fibrinogen-to-fibrin cascade that enables bacteria to be coated by fibrin clots which prevents phagocytosis
Phagocytosis
Phagocytes engulf or ingest other living cells or particles.
The destruction of what is a virulence factor against immune system?
Destruction of phagocytes with production of leukocidins.
Destruction of T lymphocytes.
Antigenic drift
Results of point mutations causing minor changes in the spike proteins.
Antigenic shift
Gene re assortment results in major changes in spike proteins.
Main virulence factors for porphyromonas gingivalis (periodontitis)
Fimbriae- modify and stimulate immune responses such as cytokine secretion and inhibition in the periodontium (tissue breakdown).
Gingipains- exoenzyme produced by p.gingivalis which breaks down structural proteins of periodontium.
Cariogenicity
Ability of a substance or organism to cause tooth decay
Acidogenicity
Producing acid or causing acidity
Main virulence factors of associated with cariogenicity and what do they do and cause
Adhesion
Acidogenicity
Acid tolerance
Work together to chance ecology of dental plaque.
Cause susceptibility to enamel demineralisation.
Cariogenic bacteria
Live in biofilm and convert sugar and starch into acid that dissolve calcium from enamel.
An increase causes a quick drop in pH levels.
Where does herpes simples virus hide from immune system and how do they emerge
In neurons and non neuronal cells.
Emerge as pathogenic form when immune resistance is low.
Name for cold sore
Herpes labialis
Most common etiological factor of opportunistic human fungal infections
Candida albicans - pathogenic yeast-like fungus
Main virulence factors of Candida albicans
Exoenzymes; secretes aspartyl proteases which breakdown proteins.
Adhesions.
Pleomorphism; responds and adapts to changing environmental conditions.
Which type of antigenic variation results in a major change in spike proteins due to gene reassortment?
Antigenic shift
In order to survive, pathogens require a source of nutrients, protection from harmful elements and:
Colonization of a niche in the host
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?
Primary pathogen
Virulence factors can be described as:
Mechanisms that determine the degree to which the pathogen causes damage to a host.
A factor that helps an organism to invade a host.
Factors which enable a pathogen to infect a host
What kind of virulence factors are proteases, nucleases, phospholipases and glycohydrolases?
Exoenzymes
Which of these virulence factors act as adhesins?
Proteins F and A
Pili
Fimbraie
Which of these virulence factors assist in promoting colonization of the host?
Adhesins
Which of these virulence factors enable damage to be caused to the host?
Toxins and exoenzymes
Which virulence factor does Porphyromonas Gingivalis use which leads to disregulated immunity in the gingival tissues and breakdown of the structures around the teeth?
Fimbraie and exoenzyme Gingipains
