Skin infections Flashcards
name 6 reasons skin is intrinsically resistant to infection
- low water content • low pH
- low temperature • high salt
- fats and fatty acids • microbiota
name some of the normal skin microbiota
mostly bacteria but some yeasts. Staphylococcus epidermidis • Staphylococcus aureus • diptheroids • streptococci Candida
types of bacterial skin infections. give examples of each (3)
Localised infections: folliculitis, abscess.
Spreading infections: impetigo, cellulitis.
Necrotising infections: fasciitis
what happens in folliculitis and what is most common cause?
blockage of hair follicle caused by Staph A
which staph can cause UTIs?
S. saprophyticus
S. aureus produces a vast array of virulence factors to enable it to overcome immunity. name 5
- Binds to damaged tissues via adhesins
- inhibits chemotaxis
- Inhibits phagocytosis
- If ingested by PMNs, can resist killing
- forms biofilms
key feature that differentiates CA-MRSA from HA-MRSA
CA-MRSA has the gene for PV-leukocidin
another name for impetigo and its 2 likely causative organisms?
staph a. or GAS. School sore
cause of bullous impetigo
staph A.
2 other names for GAS
strep pyogenes or Group A beta haemolytic strep
what are Erysipelas & cellulitis and their most likely cause?
E = rapidly spreading superficial reddening of skin with fever and pain. C = similar but involves subcutaneous fat. both most likely caused by GAS
most common causes of necrotising faciitis and gangrene.
NF = GAS and anaerobes (including clostridium).
Clostridium perfringens for gangrene
M protein is a virulence determinant associated with which organism
GAS
what is a NET? which bacteria can overcome this and how
Neutrophil Extracellular Trap - the neutrophil essentially forms a net of DNA arround the organism.
GAS can overcome this with a DNAse
3 ways GAS causes damage?
Direct: cytolethal toxins and enzymes.
Superantigens. Activation of autoimmunity
what kind of bacteria are clostridia
GPR and anaerobes
what kind of trauma is pseudomonas infection likely to result (2)
diabetic foot ulcer and burn
name 2 viruses that cause skin infection
HSV and VZV
