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
