C3 Flashcards
Define virulence factor
Molecules expressed & secreted that enable them to colonise the host, evade & inhibit the immune response of host
Factor that enhances transmission
- Multiple sources & high endemicity
- High conc released into environment media
- High carriage rate
- Proliferate & adapt to different host
- Seasonality & climatic effects
- Antibiotic resistance
Define virulence properties
Structure or chemical constituents that contribute to pathophysiology
Example of virulence properties
- Outer cell membrane of Gram -ve
- Exotoxin
- Pili
- Invasins
Host factor in pathogen transmission
- Age
- Immune status
- Pregnancy
- Genentic background
- Nutritional status
What is adhesin
Found on cell wall of bacteria that bind to specific receptor molecule on surface of host cell
Example of adhesin
- Fimbriae
- Capsule
- Biofilm
- Fibronectin binding protein (FBP)
Explain the relationship of surface structure & virulence
- Bacterial surface antigen altered by mutation
- Progeny are no longer recognised by immune response
- Result in renewed virulence
Colonisation factor
- Ability to use motility to contact & disseminate host
- Ability to adhere & resist physical removal
- Ability to invade host cell
- Ability to compete for iron & other nutrients
- Ability to resist innate immune defense
- Ability to evade adaptive immune defence
Virulence factor in bacteria encoded on
- Chromosomal DNA
- Bacteriophage DNA
- Plasmid
- Transposons
How virulence factor transmit
- Bacteria infect by bacteriophages
- Integrate its genome into bacterial chromosome
- Serve as basis of toxin production
Define antigenic drift & antigen shift
Antigenic drift
- Result of point mutation causing slight mutation in spike protein hemagglutinin (H) & neuroamidase (N)
Antigenic shift
- Major change in spike protein due to gene reassortment
- 2 different influenza infect same host
Antigenic variation result in
Continual emergence of new strain that immune system not recognise
Explain tumor necrosis factor
- Release by Gram -ve bacteria
- Involved inflammation & fever
- Bind with blood capillaries to increase permeability
- Cause edema or swelling
Class & example of exoenzyme
- Glycohydrolases: Hyaluronidase
- Nucleases: DNAse
- Phospholipases: Phospholipase
- Protease: Collagenase
Function of exoenzyme
Facilitate invasion or support its own growth & defend against immune system
Function of Hyaluronidase, DNAse, phospholipase & collagenase
Hyaluronidase & Collagenase
- Allow pathogen to pass through tissue layer & spread in the body
DNAse
- Degrade extracellular DNA to escape & spread through tissue
Phospholipase
- Degrade cell membrane
- Lyse target cell (RBC, WBC, tissue)
Lipid A trigger
Inflammatory response
What happen when concentration of endotoxin is high
- Cause excessive inflammatory response
- Result in low blood pressure, multi organ failure
How to inactivate endotoxin & exotoxin
Endotoxin
- Heat stable
- 121C & 45 mins to inactivate
Exotoxins
- Heat labile
- 41C
Explain exotoxin
- Target specific receptors on specific cell
- Damage cell through unique molecular mechanisms
Characteristics of endotoxin & exotoxin
Endotoxin
- Gram -ve
- Lipid A
- General effects
- Heat stable
- LD50: High
Exotoxin
- Gram +ve & -ve
- Protein
- Specific
- Heat labile
- LD50: Low