S6) Surface Infections Flashcards
Define a surface
A surface is an interface between a solid and either a liquid or a gas
In terms of the infection model for surface infections, identify and describe the two types of surfaces involved
- Skin: epithelium, hair, nails
- Mucosal surfaces: GI, GU, resp, conjunctival
Identify the types of micro-organisms found on the skin and provide examples
- Viruses – papilloma, herpes simplex
- Bacteria – S.aureus, Coagulate negative staphylococci, Enterobacteriaceae
- Fungi – yeasts, dermatophytes
- Parasites – mites
Identify 5 different ways people get surface infections and provide examples of each
- Microbiota
- Invasion e.g. Strep pyogenes in pharyngitis
- Migration e.g. E.coli in UTI
- Inoculation e.g. Coagulate negative staphylococcus in prosthetic joint infection
- Haematogenous e.**g. viridans Strep in endocarditis
Provide some examples of external natural surface infections
- Cellulitis
- Pharyngitis
- Conjunctivitis
- Gastroenteritis
- UTI
Provide some examples of internal natural surface infections
- Endocarditis
- Septic arthritis
- Osteomyelitis
- Empyema
Provide 5 medical devices/procedures which could give rise to prosthetic surface infections
- Intravascular lines
- Peritoneal dialysis catheters
- Prosthetic joints
- Cardiac valves
- Pacing wires
What are the causative organisms for prosthetic valve endocarditis?
- Prosthetic valve endocarditis > 1 year post-operation: viridans Streptococci, Staph aureus
- Prosthetic valve endocarditis < 1 year post-operation: Coagulase negative staphylococci
What are the causative organisms for prosthetic joint infections?
- Coagulase negative staphylococci
- Staphylococcus aureus
What are the causative organisms for cardiac pacing wire endocarditis?
- Coagulase negative staphylococci
- Staphylococcus aureus
In 4 steps, outline the pathogenesis of surface infections
⇒ Adherence to host cells / prosthetic surface
⇒ Biofilm formation
⇒ Invasion and multiplication
⇒ Host response
Identify and describe the two possible host responses in the pathogenesis of surface infections
- Progenitor: neutrophils → pus
- Granulomatous: fibroblasts, lymphocytes, macrophages → nodular inflammatory lesions
Explain the process involved in biofilm formation in the pathogenesis of surface infections
Biofilm formation is a process whereby microorganisms irreversibly attach to and grow on a surface and produce extracellular polymers that facilitate attachment and matrix formation
In detail, explain how micro-organisms cause disease
In management of a surface infection, outline the diagnosis of it
Aim is to identify infecting organism and its antimicrobial susceptibilities:
- Blood cultures
- Tissue/prosthetic material sonication and culture
