Overview of adhesion

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Lecture 2
Interactions with host surfaces II Adhesion

• Overview of adhesion
• Types of bacterial adhesins
• Specificity of adhesion
• Consequences of adhesion

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Lecture 2
Interactions with host surfaces II Adhesion

• Overview of adhesion
• Types of bacterial adhesins
• Specificity of adhesion
• Consequences of adhesion

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Overview of Bacterial Pathogenesis
Encounter
Adhesion to a surface
non-specific host defences
(Invasion of tissues)
Inflammation
Cell tissue damage
specific host defences
Multiply spread
Exit
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Overview of interactions with host surfaces

• Nonspecific adhesion

• Specific
• adhesion

• overall, surface interactions
• entrapment in mucin

gt 50 nm
10 20 nm
lt 2 nm
lt 1.0 nm
Hydrophobic interactions
Specific interactions
Electrostatic repulsion
Van der Walls
Weak attractive
adhesin
receptor
Weak long-range attractive
easily disrupted
Very strong irreversible
Repulsion reduced by (a) high ionic strength (b)
small diameter
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Nonspecific 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 adhesion
EPEC adhering to an intestinal epithelial cells
Bordetella pertussis on to ciliated tracheal cell
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Fimbriae on surface of a human ETEC strain

• Strains may express gt 1 distinct type of
  fimbriae,
• with different receptor specificities

CS3 thin, flexible
CS1
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Consequences of adhesion
3. Colonize surface and form a biofilm

• In contrast to localised colonies, some
  pathogens
• can form a spreading surface layer a
  BIOFILM

• bacteria encased in a polysaccharide slime that
  aids
• attachment and protects bacteria.

• Simple biofilm comprises a single species

• Staphylococcus epidermidis
• biofilm on a catheters

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Complex Biofilms

• Comprise multiple species

• Bacterial co-aggregation

• Some species produce polysaccharides, trapping
  others

Example Dental plaque