Necrotising Infections Flashcards
Conditions of skin?
Dry
Acidic
Salty
Colder
Which areas of skin have different conditions?
Crevices are more moist
Sebaceous areas are more oily
Sweat as protection against bacteria?
Osmotic pressure
Skin adaption to remove cells?
Shedding
What type of organisms are present on skin and why?
Gram-positive
Survive well in arid conditions
What is usually the cause of skin infections?
Trauma - Bites, cuts, ulcers
Where do skin pathogens come from?
May colonise body or be spread from another person
Give 4 examples of deepening skin infections and causative organisms
Impetigo - Infects epidermis, S. pyogenes and S. aureus
Erysipelas - Infects dermis and can spread to SC fat, S. pyogenes
Cellulitis - Infects dermis and SC fat, S. pyogenes and S. aureus
Necrotising Fasciitis - Infect SC fat and fascia, S. pyogenes and anaerobes
What is the fascia?
Surrounds muscle, connective tissue
Treatment of Nec Fasc?
Treated with rigorous broad spec. antibiotics, possibly debridement and surgery
Why does Nec Fasc have to be treated quickly?
S. pyogenes moves through skin layers quickly
Presentation of Nec Fasc?
Red, hot, swollen, very painful
No real presentation, localised pain may be indicator
Predisposition to Nec Fasc? (8)
1) Trauma/surgery
2) Diabetes
3) IV drug use (aseptic)
4) Elderly
5) Smoking
6) Immunocompromised
7) Female
8) Bruising
Nec Fasc mortality?
Around 30%
Antibiotic to reduce chance of sepsis?
Clindamycin
Virulence factors of S. pyogenes? (4)
1) Breakdown of NET
2) Phagocyte apoptosis
3) Prevents neutrophil recruitment
4) Hyaluronic acid to prevent recognition
What is needed for pathogen to cause infection?
Immune invasion and evasion
Most common superficial infection?
Impetigo
Common cause of impetigo?
S. aureus falls from nose onto face, infects when trauma
When is impetigo incidence highest? Why?
Summer
Insect bites, skin exposure
Types of impetigo? Incidence?
Non-Bullous, 70%
Bullous, 30%
Pathogenesis of bullous impetigo? Characterisation?
Exfoliative toxin A targets desmoglein-1 (holds skin layers together, cutting allows spread through skin)
Localised loss of stratum corneum
Infectious vacuoles
Treatment of bullous impetigo?
Topical fusidic acid TDS 5/7
Widespread: Flucloxacillin QDS 7/7 or clarithromycin BD 7/7
When would swabs be taken in impetigo?
Treatment resistant
