Pathogenicity Flashcards
What is a pathogen?
An organism capable of causing disease
What is a commensal
Bugs that don’t cause harm but live/exist in the body
They are part of the normal flora
What is pathogenicity?
The ability to cause disease
What is virulence?
The ability to cause severe disease
What does ubiquitous mean?
They are everywhere
What is an opportunist pathogen?
When in the right environment with the right conditions they will cause disease/damage
What are the 5 divisions of microorganisms?
- Bacteria
- Fungi
- Viruses
- Prions
- Parasites
What is colonisation?
When microbes find a new host and start to multiply
What is the bodies ‘normal flora?
When a balance develops between colonised microbes and humans
What is the name for when microbes cause disease?
Infection
What is an endogenous infection?
If the source of microbe is patient’s own flora - organisms in the body that cause infection
What is an exogenous infection?
If source of microbes is flora from outside the patient’s body - risk you get from other individuals - transmission of organisms
What is Koch’s postulates - the germ theory of disease?
If you take someone with a disease and take a sample from the patient - grow in pure culture to prove only organism there - put into animal model and show that animal then develops same disease: shows that one organism causes specific disease
How can diseases be transmitted?
- Person-to-person
- Fomites
- Insects
- Water
- Food
How can diseases be transmitted from person-person?
- Contaminated blood or bodily fluids
- Touch
- Air
- Saliva
What are fomites?
Objects or materials that are likely to carry infection such as clothes, utensils or furniture
What is the function of a capsule?
Layer that surrounds a prokaryotic cell
What is the function of fimbriae?
cells ‘arms’ that can attach to things
What is the function of a flagellum?
Allows movement of the cell (tail)
What is the function of inclusion granules?
Stored nutrients, secretory products and pigment granules
What is the function of membranous invagination?
The membrane folding in on itself and forming membranous organelles
What are some encapsulated infections?
- Meningitis
- Pneumonia
- Sinusitis
Name some capsular functions?
- Mediate adhesion
- Immune evasion
- Protect from drying up (desiccation)
- Reserves of carbohydrate
- Capsular material gives rise to ‘capsular antigens’
- Encapsulated bacteria gives rise to smooth colonies
What is an exotoxin?
Release from a living bacteria cell into its surroundings
What is an endotoxin?
A toxin present inside a bacterial cell that is released when the cell dies
What is tetanus also known as?
Locked jaw - muscles are over stimulated (highly deadly)
What is Fimbriae/pili, colonisation factors contribution to virulence?
Adhesion, antiphagocytic
What are capsule/slimes contribution to virulence?
Adhesion, protection against phagocytosis and complement, camouflage from immune system
What is peptidoglycan’s contribution to virulence?
Immunomodulation, induction of inflammatory mediators
What is LPS/endotoxins contribution to virulence?
Protection against compliment, induction of inflammatory cytokines: endo-toxic shock/ system inflammatory response syndrome
What does Teichoic acid, secondary cell wall carbohydrates contribution to virulence?
Adhesion, sequestration of divalent cations, induction of inflammatory mediators
What does flagella, axial filaments contribution to virulence?
Chemotaxis, penetration of mucus
What are outer membrane proteins contribution to virulence?
Adhesion. Sequestration of iron. Invasion. Intracellular survival
What are surface proteins contribution to virulence?
Adhesion, binding Fc region of immunoglobins
