Lec 6 - Bacterial adhesion and colonisation Flashcards
What is AFM and contact angle?
AFM = measure of surface roughness
Contact angle = measures wettability. large angle = hydrophobic
What bacter adhere to implant surfaces?
Stahplococci (gram -)
They are coagulase negative
Outline surface colonisation
1) attatchment
2) accumilation
3) maturation (toxin+evasion)
4) detatchment
How does bacteria attach to host cells?
Physico-chemical interactions
- Van der waal (>50nm)
- Electrostatic forces (10-20nm)
- Hydrophobic interactions (0.5-2nm)
- Direct interactions (
What are cell wall anchored (CWA) proteins?
Proteins that attatch to peptidoglycan.
These are iron-limited that bind to 2 or more ligands.
4 groups based on motifs
- MSCRAMM
- NEAT
- Three helical
- G5-E repeat
Has N and C terminal.
N - secretory sec-dependant signal sequence
C - Sorting signal
What is MSCRAMMs and its binding mechanism?
Most prevalent group of CWAs
Unique 2 adjacent IgG folded in N-terminal and Serine-aspartate repeats.
mechanism: Dock lock latch
used by SdrG, ClfA, ClfB
What is NEAT and its binding mechanism?
Near iron transporter motif protein of the CWAs
Captures haem from haemoglobin
mechanism: IsdA and IsdB
What is Three-helical?
CWAs
multifunctional
ubiquous to S.aureus
strain typing
What is G5-E?
Part of the CWAs
5 consecutive conserved glycine residues
G5 domain adopt B-triple helix-B-like fold
E region- seperate G5 tandem arrays and prevent protein misfolding
What CWA’s are involved in Nasal/skin colonisation and what do they adhede to?
ClfB: loricin/squames
IsdA, SasX : squames
What CWA’s are involved in endocarditis and what do they adhede to?
ClfA: ClfB : Thrombus
FnBPA : Thrombus (endothelium)
SraP: platelets
What CWA’s are involved in Mastitis and what do they adhede to?
FnBP : mammary glands (epithel.)
What CWA’s are involved in Pneumonia and what do they adhede to?
Protein A - lung epithelium
What CWA’s are involved in Foreign body infection and what do they adhede to?
FnBP : MRSA biofilm
What CWA’s are involved in Ocular keratitis and what do they adhede to?
Cna: enchanced colonisation/infection
What CWA’s are involved in Septic death and what do they adhede to?
ClfA, Protein A, IsdH, Sasx :
osponophagocytosis
What CWA’s are involved in Septic arthritis and what do they adhede to?
ClfA, ProteinA, Cna:
Survival in bloodstream, cartilage within joint
How are CWAs studied?
1) Culture bacteria
2) Break cell wall
3) Boil in SDS (ion)
3) Digest with lysotaphin (cov.)
4) SDS-PAGE gel
5) Western Blot using anti-sera for adhesin
What is immunogold labelling?
Locates specific adhesin on cell walls by using antibody for adhesin and secondary antibody (gold)
What is the significance of biofilm?
Protect bacteria from antimicrobials and phagocytosis
How are biofilms formed?
Polysaccharide intercellular adhesin (PIA), synthesised by icaADBC
PIA: exopolysaccharide deacylated requires all 4 genes expressed Induced by purR,sarA,luxS Down regulated by icaR
What are other factors involved in adhesion and biofilm formation?
Extracellular matrix binding protein (Embp)
eDNA and Atl proteins
Teichoic acid (cell wall)
PS/A - polysaccharide adhesin
What are detachment factors of adhered bacteria?
Mechanical forces
Production of biofilm
Destruction of biofilm (protease)
What are some evasion mechanisms of bacteria?
S. aureus:
Catalase
ProteinA (bind Fc of IgG, opsonisation)
Leukocidins (inhibit chemotaxis)
S. epidermidis:
phenol soluble modulins that induce cytokine/NFK, attractants for neutrophils and monocytes and inhibits neutrophil apoptosis.
