6. Infections on surfaces Flashcards
What is a surface?
Interface between a solid and either a liquid or a gas
What are some examples of natural surface infections?
Cellulitis, pharyngitis, UTI, pneumonia
What prosthetic surfaces can lead to infection?
Intravascular lines Peritoneal dialysis catheters Prosthetic joints Cardiac valves Pacing wires
How can the risk of infection from intravascular lines be reduced?
Silver coated lines - inhibit growth
Outline the pathogenesis of surface infections
- Adherence to host cells or prosthetic surface
- Biofilm formation
- Invasion & multiplication
- Host response -pyogenic, granulomatous
What virulence factors aid bacterial adherence to host surfaces?
Pili, frimbiae, adhesins
What are biofilms made of?
Mucopolysaccharide, protein molecules and nucleic acid
What mechanism do bacteria use to signify presence and detect others?
Qorum sensing chemicals are produced, an increased number signifies higher number of bacteria present.
What is the advantage of bacterial biofilms?
Protect against complement, neutrophils and antimicrobial attack
What 3 things does qorum sensing control?
- Sporulation
- Biofilm formation
- Virulence factor secretion
What 3 principles are involved in qorum sensing?
- Signalling molecules released- autoinducers
- Cell surface or cytoplasmic receptors
- Gene expression to increase cooperative behaviours and more biofilm production
Why does the presence of a bacterial biofilm make diagnosis more challenging?
Bacteria are in a low metabolic state, so grow poorly on agar plates.
Why does the presence of a bacterial biofilm make treatment more challenging?
Biofilm provides a barrier against antimicrobials
Low metabolic activity decreases susceptibility to antibiotics
How can bacterial infection on natural surfaces be prevented?
Maintain surface integrity
Prevent colonisation
How can bacterial infection on prosthetic surfaces be prevented?
Prevent contamination
Inhibit surface colonisation
Remove colonising bacteria
