Lec 6 - Bacterial adhesion and colonisation

Question 1

What is AFM and contact angle?

Answer 1

AFM = measure of surface roughness

Contact angle = measures wettability. large angle = hydrophobic

Question 2

What bacter adhere to implant surfaces?

Answer 2

Stahplococci (gram -)

They are coagulase negative

Question 3

Outline surface colonisation

Answer 3

1) attatchment
2) accumilation
3) maturation (toxin+evasion)
4) detatchment

Question 4

How does bacteria attach to host cells?

Answer 4

Physico-chemical interactions

• Van der waal (>50nm)
• Electrostatic forces (10-20nm)
• Hydrophobic interactions (0.5-2nm)
• Direct interactions (

Question 5

What are cell wall anchored (CWA) proteins?

Answer 5

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

Question 6

What is MSCRAMMs and its binding mechanism?

Answer 6

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

Question 7

What is NEAT and its binding mechanism?

Answer 7

Near iron transporter motif protein of the CWAs

Captures haem from haemoglobin

mechanism: IsdA and IsdB

Question 8

What is Three-helical?

Answer 8

CWAs

multifunctional
ubiquous to S.aureus
strain typing

Question 9

What is G5-E?

Answer 9

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

Question 10

What CWA’s are involved in Nasal/skin colonisation and what do they adhede to?

Answer 10

ClfB: loricin/squames

IsdA, SasX : squames

Question 11

What CWA’s are involved in endocarditis and what do they adhede to?

Answer 11

ClfA: ClfB : Thrombus
FnBPA : Thrombus (endothelium)
SraP: platelets

Question 12

What CWA’s are involved in Mastitis and what do they adhede to?

Answer 12

FnBP : mammary glands (epithel.)

Question 13

What CWA’s are involved in Pneumonia and what do they adhede to?

Answer 13

Protein A - lung epithelium

Question 14

What CWA’s are involved in Foreign body infection and what do they adhede to?

Answer 14

FnBP : MRSA biofilm

Question 15

What CWA’s are involved in Ocular keratitis and what do they adhede to?

Answer 15

Cna: enchanced colonisation/infection

Question 16

What CWA’s are involved in Septic death and what do they adhede to?

Answer 16

ClfA, Protein A, IsdH, Sasx :

osponophagocytosis

Question 17

What CWA’s are involved in Septic arthritis and what do they adhede to?

Answer 17

ClfA, ProteinA, Cna:

Survival in bloodstream, cartilage within joint

Question 18

How are CWAs studied?

Answer 18

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

Question 19

What is immunogold labelling?

Answer 19

Locates specific adhesin on cell walls by using antibody for adhesin and secondary antibody (gold)

Question 20

What is the significance of biofilm?

Answer 20

Protect bacteria from antimicrobials and phagocytosis

Question 21

How are biofilms formed?

Answer 21

Polysaccharide intercellular adhesin (PIA), synthesised by icaADBC

PIA:
exopolysaccharide deacylated
requires all 4 genes expressed
Induced by purR,sarA,luxS
Down regulated by icaR

Question 22

What are other factors involved in adhesion and biofilm formation?

Answer 22

Extracellular matrix binding protein (Embp)

eDNA and Atl proteins

Teichoic acid (cell wall)

PS/A - polysaccharide adhesin

Question 23

What are detachment factors of adhered bacteria?

Answer 23

Mechanical forces

Production of biofilm

Destruction of biofilm (protease)

Question 24

What are some evasion mechanisms of bacteria?

Answer 24

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.