Infections on Surfaces

Question 1

Describe the range of natural surface infection

Answer 1

Cellulitis (inflam subcutaneous connective tissue), 
pharyngitis, 
conjunctivitis, 
gastroenteritis, 
UTI, 
septic arthritis, 
empyema (pus in body cavity)

Question 2

Outline the range of prosthetic surface infections

Answer 2

IV lines: breach skin, peritoneal dialysis catheters,
prosthetic joints: coag –ve staph,
cardiac valves: endocarditis,
pacing wires: coag –ve staph, endovascular graphs

Question 3

Describe the importance of mucosa flora

Answer 3

Effective at keeping most flora MO at bay, sustaining normal mucosal environment

Question 4

Describe the pathogenesis of infections at the surface

Answer 4

Attraction by ionic charge can attract bact to site, 
adherence, 
biofilm formation, 
invasion/multiplication, 
host response (pyogenic, granulomatous)

Question 5

Explain a ‘biofilm’ and the implications for an infection on a surface

Answer 5

Extracellular polymeric substance (EPS), imbeds bacteria = result of quorum sensing chemicals (when chem high enough = phenotype changes from planktonic to sessile form), gullies and channels allow for supply of nutrients for bact – protects from host defences/antimicrobial attack

Question 6

What is quorum sensing?

Answer 6

Regulation of gene expression in reponse to fluctuatings in cell population density

Question 7

Describe the management of infected surfaces

Answer 7

Identify MO present, blood culture, material sonication, antibacterials, remove prosthetic, surgery

Question 8

What are the challenges when trying to manage a surface infection?

Answer 8

Poor Abx penetration into biofilm, low met activity = not very sensitive to Abx, danger/diff of surgery

Question 9

Outline some preventative measures for surface infections

Answer 9

Maintain surface integrity: skin/gum, laminar flow surgery theatres, prevent colonisation, remove colonised

Question 10

What is a surface?

Answer 10

Interface between a solid and either a liquid or gas