S7 Infections on Surfaces Flashcards
What sort of surfaces are found on a patient?
- skin - epithelium, hair, nails
* mucosal surfaces - conjunctival, gastrointestinal, respiratory genitourinary
How do people get infections from themselves?
- invasion
- migration
- inoculation
- haematogenous
What are some examples of external natural surface infections?
- cellulitis
- pharyngitis
- conjunctivitis
- gastroenteritis
- UTI
- pneumonia
What are some examples of internal natural surface infections?
- endovascular (endocarditis, vasculitis)
- septic arthritis
- osteomyelitis
- empyema
Where can you get prosthetic surface infections?
- intravascular lines
- peritoneal dialysis catheters
- prosthetic joints
- cardiac valves
- pacing wires
- endovascular grafts
- ventriculo-peritoneal shunts
What are some types of microbes that can cause prosthetic valve endocarditis?
- streptococci
- enterococcus
- staph aureus
- candida
- coagulate negative staphylococci
What microorganisms can cause prosthetic joint infections?
- coagulate negative staphylococci
* staphylococcus aureus
What microorganisms can cause cardiac pacing wire endocarditis?
- coagulate negative staphylococci
* staphylococcus aureus
What is the process of pathogenesis of infections at surfaces?
- Adherence to host cells/prosthetic surface
- Biofilm formation
- Invasion and multiplication
- Host response - pyogenic (neutrophils) or granulomatous (lymphocytes, macrophages)
What structure on microbes allows them to bind to surface receptors on host cell membranes?
Pili or fimbriae (protein strands)
What is a biofilm?
When microbes join together and produce a ‘slime layer’ which acts as a protective layer against immune cells/antibodies and complement proteins
What is quorum sensing?
Communication between microbes when there are enough microbes present
What does quorum sensing control?
- spore formation
- biofilm formation
- virulence factor secretion
What are the principles of quorum sensing?
Microbes release signalling molecules (autoinducers - AI) that bind to cell surface/cytoplasmic receptors and cause changes to gene expression (cooperative behaviours of microbes and more AI production)
How do you diagnose infections due to microbes on surfaces?
What are the challenges?
- blood cultures
- tissue/prosthetic material ultrasound and culture
Adherent organisms and small colony variants (not very virulent but are persistent/low metabolic state
What is the treatment for infections caused by microbes on surfaces?
What are the challenges?
- antibacterials
- remove the prosthetic material
- surgery - cute out infected material
Poor antibacterial penetration into biofilm, low metabolic activity of biofilm microorganisms, complications of surgery
How can you prevent infections occurring on surfaces?
Natural surfaces
- maintain the surface integrity
- prevent bacterial surface colonisation
- remove colonising bacteria
Prosthetic surfaces
- prevent contamination
- inhibit surface colonisation
- remove colonising bacteria
How do microbes cause disease - what are the steps? What are the virulence factors? What type of host cell damage can occur?
- Exposure 2. Adherence 3. Invasion 4. Multiplication 5. Dissemination
- exotoxins (cytolytic, AB toxins, superantigens, enzymes)
- endotoxins
- direct
- due to host immune response
