Skin + Soft Tissue Infection Flashcards
What bacteria normally colonise the surface of the skin?
Staphylococci -> staph aureus (coagulase +ve)
Streptococci-> group A
Corynebacteria
Gram negatives in hospitalised patients (i.e. enterobactero)
-more prominent on thoracic or abdominal skin when lying in bed
What innate skins defences prevent infection from colonising bacteria under normal conditions?
Macrophages
Langerhans cells
Lymphocytes
Antibodies
What is impetigo?
Staph aureus infection of superificial layer of face
Presents as “golden-crust” appearance
What is cellulitis?
What are predisoping factors for cellulitis?
Where does cellulitis most commonly effect?
Infection of skin and subcutaneous tissues
(Anything causing breach of innate defences of skin) Poor blood supply -PVD -Diabetes -venous insufficiency -VV -peripheral oedema -lymphoedema
Hyperglycaemia due to poorly controlled DM
Immunosuppression
Arms and legs in adults
Face more common in children
Why is diabetes a risk factor for cellulitis?
Diabetes can cause reduces blood supply to region due to causing small vessel disease
High glucose:
- impaired neutrophil function
- provides environment for bacteria to multiply
What leads to S aurea being able to penetrate skin surface?
Cut /stratch Ulcer Athletes foot Eczema Burns Foreign bodies i.e. Cannulas or drains
How might someone with cellulitis present?
At site = UNILATERAL
- Erythema
- Warmth
- Pain
- Swelling
- bullae (fluid-filled blisters)
Systemic: (cytokine driven)
- Fever
- chills
- malaise
Consider how might have entered
Look for predisposing factors
What investigations would be done for cellulitis?
D-dimer or Doppler if wanting to rule out DVT
FBC + CRP-> may be raised Culture blister fluid Blood cultures (taken if febrile or showing signs of sepsis)
Imaging only if considering deeper problem i.e. abscess
What are possible differential diagnosis for cellulitis?
How can you differentiated?
Erysipelas
- dermarcated and raised lesion of the dermis
- streptococci causing
- treated with penicillin
Lymphangitis
-red darcated line which follows the underling lymphatics
How is cellulitis managed?
Antibiotics
- empiric with coverage of s aureus, beta haemolytic and streptococci
- course as long as it takes for infection to clear
- dependent on MRSA status
Analgesia
Elevation of affected limb to reduce the swelling
Fluids
Treat predisposing factor
What is the key factor when deciding which antibiotics to treat cellulitis with?
Which antibiotics are indicated in each case?
MRSA status
MRSA +ve/risk of +ve
- IV vancomycin
- oral co-trimoxazole/clindamycin (has good bioavailability and soft tissue penetration)
MRSA -ve
- Beta-lactams i.e. IV/oral flucloxacillin or cephalosporins
- Lincosamides/macrolides i.e. clindamycin IV/oral
What can be done to prevent cellulitis?
Reduce skin bacteria via skin hygiene, MRSA eradication, prophylactic antibiotics
Prevent skin breaks
- wound healing and cleaning
- treat eczema /athletes foot
Maximise defenes
- treat vascular disease
- reduce oedema
- good diabetes control
What is necrotising fasciitis?
What is a potent cause?
How might someone present?
How is it managed?
Severe infection of the deep fascial layers
Group A streptococci
Disproportionate pain with dusky, bruised appearance
Surgical emergency
- aggressive debridement
- antibiotic- clindamycin
What is pyomyositis?
How does it present?
How is it investigated?
How is it managed?
Acute bacterial infeciton of skeletal muscle due to staph aureus infection (rare)
Muscle pain Tenderness Swelling Associated with tropics Tends to have preceding history of trauma or vigorous exercise i.e. hyperaemia which allows organisms to enter
MRI and CT
-can be used to define muscle oedema, large collections an guide drainage
Drainage
Antibiotics
