Intro To Pathognesis Flashcards
3 types of pathogen
Primary
Secondary
Opportunistic
What is a primary pathogen
Pathogen that is likely to cause infection if encounters naive host
“Once a pathogen always a pathogen”
What is secondary pathogen
Need help to cause infection- More likely to cause disease once the ground has been
prepared for them by another pathogen
What is an opportunistic pathogen
Pathogens that don’t normally cause infection but can if the host defences are compromised.
Pathogenesis meaning
Processes/mechanisms of disease development
All things that bacteria/ host do that cause pathology
Virulence meaning
Measure of capacity to damage/kill host
How harmful pathogen is
Infectivity definition
How easy it is to catch disease
Reflects ability of organism to enter, colonise and survive in host (organism can have low virulence but high infectivity)
Define Virulence factors
Component of bacteria that’s involved in pathogenesis, virulence or infectivity
-the molecules that assist the bacterium in colonizing the host at the cellular level
Koch’s 4 postulates
-The organism or it’s products should be found in all individuals with the disease
-The organism should be isolated and be maintained in pure culture
-The pure culture inoculated into an individual should cause the disease
-The organism should be re-isolated in pure culture
Do Koch’s postulates apply to all infectious disease?
No, as different types of pathogens exist e.g secondary pathogens which wont cause disease all the time
What does multi factorial virulence mean?
Needs multiple virulence factors to cause disease (some bacteria wont work without correct combination of virulence factors)
What is bacterial adhesion
process that allows bacteria to attach or adhere to other cells and surfaces. Adhesion is an important step for colonization of a new host or environment and can contribute to bacterial pathogenesis.
2 types of colonisation life cycles
Intracellular vs extracellular
Describe steps of extracellular pathogen lifecycle
1.Attachment
2.Resist phagocytosis
3.Resist action of complement
4.Acquire nutrients (iron/antibodies)
Examples of extracellular life cycle pathogens
E.coli
A.pleuropneumoniae
B.anthracis
Clostridia sp.
S.aureus Streptococci sp.
Mycoplasma sp.
Name steps of intracellular lifecycle colonisation
- Attachment
- Invasion
- Resist intracellular destruction
- Acquire nutrients
Examples of intracellular pathogens
Mycobacteria sp.
L. monocytogenes
Salmonella sp.
Brucella sp.
Chlamydia sp.
Rickettsia sp.
Defences against extracellular pathogens
Activation of the complement system, phagocytosis, and inflammatory response
Common virulence factors of extracellular pathogens
• Adhesins
• Anti-phagocytic factors
– Capsules, surface proteins, toxins
• Anti-complement
– Inhibit: activation, deposition, function
– Many, diverse mechanisms
• Nutrient acquisition systems
– eg, iron uptakes systems
What are capsules usually made of?
Acidic polysaccharides
What are exotoxins and what do they do
A toxin secreted by bacteria
-cause damage to the host by destroying cells/ lyse RBC’s in vivo/ lyse phagocytes and affect their function
What does mannheimia haemolytica leukotoxin do? (Exotoxin)
Act exclusively on leukocytes from ruminants
Damage to neutrophil leads to release of tissue destroying enzymes and attracts more neutrophils. Also affect platelets resulting in thrombosis
What are DNAse secreted from pathogen used for
To escape NETs
Which nutrient is essential to most bacteria for replication/infection?
Iron
Many intracellular pathogens can survive in what cell type?
In macrophages
Advantages of intracellular pathways surviving in macrophages
Long lived cell
Haven from extracellular defences of host
Rich supply of nutrients
Dissemination
Survival strategies of intracellular bacteria in macrophages and which pathogen can do what strategy
Escape from the phagosome
L.monocytogenes, Rickettsia sp. Shigella sp.
Prevent acidification
M.tuberculosis, L.pneumophila
Prevent fusion
M.tuberculosis, Salmonella sp., Brucella sp.
Survival in phagolysosome
Coxiella Burnetti
