Lecture 2
description
Transcript of Lecture 2
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Lecture 2
• Overview of adhesion • Types of bacterial adhesins
• Specificity of adhesion
• Consequences of adhesion
Interactions with host surfaces II: Adhesion
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Lecture 2
• Overview of adhesion • Types of bacterial adhesins
• Specificity of adhesion
• Consequences of adhesion
Interactions with host surfaces II: Adhesion
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Adhesion to a surface
Multiply + spreadspecific
host defences
Cell & tissue damage
non-specific host defences
Exit
Inflammation
Overview of Bacterial Pathogenesis
EncounterEntry
First-line
Sources +Transmission
(Invasion of tissues)
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Van
der
Wal
ls
> 50 nm 10 – 20 nmEl
ectro
stat
icre
puls
ion
< 2 nmHydrophobicinteractions
< 1.0 nmSpecific
interactions
easilydisrupted
Very strongirreversible
Weak long-rangeattractive
Repulsion reduced by:(a) high ionic strength(b) small diameter
Nonspecific adhesion
Wea
k at
tract
ive
adhesin
receptor
Overview of interactions with host surfaces
• overall, surface interactions• entrapment in mucin
Specific adhesion
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Nonspecific adhesionNonspecific adhesion Weakly adhering bacteria - easily removed by physical shear forces or washing
May allow colonisation of surfaces not subject to strong physical/washing forces (e.g. skin, vagina)
Not sufficient to colonise e.g. urinary tract, small intestine, etc
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Specific adhesionSpecific adhesion
EPEC adhering to an intestinal epithelial cells
Bordetella pertussis onto ciliated tracheal cell
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Fimbriae on surface of a human ETEC strain
CS3 – thin, flexibleCS1
Strains may express > 1 distinct type of fimbriae, with different receptor specificities
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3. Colonize surface and form a biofilmConsequences of adhesionConsequences of adhesion
In contrast to localised ‘colonies’, some pathogens can form a spreading surface layer – a ‘BIOFILMBIOFILM’
‘Simple’ biofilm: comprises a single species
• Staphylococcus epidermidis biofilm on a catheters
• bacteria encased in a polysaccharide slime that aids attachment and protects bacteria.
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‘ ‘Complex’ Biofilms:Complex’ Biofilms:
Bacterial ‘co-aggregation’ Some species produce polysaccharides, ‘trapping’ others
Example: Dental plaque
Comprise multiple species