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21 Cards in this Set
- Front
- Back
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Pathogenesis
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Mechanism of disease production
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Virulence
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Relative ability of pathogenic organism to cause disease
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Pathogen
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Organisms that cause disease
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Commensals
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Organisms that live in harmony with us
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Saprophytes
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Organisms that live in the environment
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Outcomes of encounter between host and parasite
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Acute illness --> immunity
Asymptomatic Colonisation Chronic illness Latency |
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Barriers to MOs
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Anatomical barriers
Flushing mechanisms Chemicals Microbial colonisation resistance |
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When do MOs cause disease
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When host defences fail
Organisms overcome host defences |
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Defence failures
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Wounds
Catheters H2 blockers Antibiotic use |
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Pathway of overcoming host defences (6)
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Attach
Penetrate Spread Survive/Multiply Cause damage Exit |
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ATTACHMENT/start of infection (4)
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Skin: injury/insect vectors
Mucosal surfaces: thin epithelia Non-specific Lock and key |
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PENETRATE (3)
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Some must enter cell to survive
Some stay on surface Invasion common/short lived |
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SPREAD (4)
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Blood
ECF/Lymph Nerve cells Body spaces |
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How do they SURVIVE AND MULTIPLY (3)
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Must resist complement, phagocytes and spleen
EC survival: capsules/antiphagocytic mechanisms IC survival: phagocytes and other cells |
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CAUSE DAMAGE (3)
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Direct: cell damage/exotoxins
Indirect: Endotoxin/Immunopathology/Systemic effects |
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Bacterial Toxins (2)
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Exotoxins: bacterial protein toxins with a variety of actions
Endotoxins: LPS component of G-ve bacteria that trigger host mechanisms |
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Exotoxin Mechanisms (6)
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Lyse enzymes (Clostridium perfringens)
Pore formation (Staph. aureus) Inhibit protein synthesis (C. diptheriae) Hyperactivation of cell (V.cholerae) Block inhibition of synapse (Cl.tetani) Block synapse transmission (Cl. botulinum) |
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Endotoxin mechanisms (3)
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Activation of endothlial cells, mast cells, platelets, clotting, complement, macrophages
TNF, IL release Fever, shock, DIC, hypoglycaemia |
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Immunopathogenesis (3)
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Inflammation
Hypersensitivity Immune destruction of virus infected cells |
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EXIT/Modes of spread (7)
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Venereal
Respiratory Faecal-oral Vertebrae Environment Hands |
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PERSISTENCE (4)
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Persistent shedding after acute infection
Latent infection Persistent slow infection following acute infection Slow infection with no acute stage |
