Skin and Soft Tissue Infection

Question 1

What is impetigo and how does it present?

Answer 1

• Golden encrusted skin lesions with inflammation localised to the dermis
• Signs/symptoms include vesicles/bullae, crusting and erythema
• Can be classified as bullous (always S. aureus) and non-bullous
• Most common in children and is contagious
• Caused by S. aureus and S. pyrogenes
• Usually self-limiting but can treat with topical fusidic acid or systemic antibiotics if required

Question 2

What is a soft tissue abscess and how does it present?

Answer 2

• Infection within the dermis or fat layers with development of walled off infection and pooled pus
• Limited antibiotic penetration
• Best treatment is always surgical drainage
• Antibiotics not usualyl required if fully drained and no surrounding cellulitis

Question 3

What is cellulitis and how does it present?

Answer 3

• Infection involving dermis
• Most commonly begins on lowe limbs
• Often tracks throught he lymphatic system and may involve localised lymph nodes
• May be associated with systemic upset
• Usually caused by β-haemolytic streptococci (Gp A Strep most common) and S. aureus

Question 4

How is cellulitis classified?

Answer 4

• Enron Classification
• I) Patient not systemically unwell and no significant co-morbidities (A no antibiotics or <48hrs, B failed to respond to antibiotics >48hrs)
• II) Patient systemically unwell or has significant co-morbidities which may complicate or delay resolution of infection
• III) Patient has significant systemic upset or unstable co-morbidities that will interfere with response to treatment or limb threatening vascular compromise
• IV) Presence of sepsis or severe, life threatening complications

Question 5

Management of cellulitis

Answer 5

• FBC (raised WCC) and cultures to diagnose
• Stage I/IA) 1st flucloxaxillin PO and 2nd doxycycline PO
• Stage IB/II) 1st flucloxaxillin IV and 2nd vancomycin IV
• Stage III/IV) Require hospital admission for IV therapy and consideration or surgical intervention

Question 6

What are the clinical features of Streptococcal toxic shock?

Answer 6

• Caused by toxin producing Group A Streptococcus
• Primary infection typocalls within the throad or skin/soft tissue
• Patient’s with present with localised infection, fever and shock
• Often diffuse, faint rash over body/limbs

Question 7

How is Streptococcal toxic shock treated?

Answer 7

• Surgery (drain abscesses)
• Antibiotics (penicillin may be ineffective, add clindamycin to reduce toxin production)
• Consider human immunoglobulin

Question 8

What are the clinical features of necrotising fasciitis?

Answer 8

• Life threatening soft tissue infection
• Rapidly progressive with extensive tissue damage requiring extensive surgical debridement
• Pain out of proportion to clinical signs
• Presence of visible necrotic tissue
• Severe systemic upset
• Imaging may demonstrate fascial oedema and gas in soft tissues
• Type 1 - Polymicrobial (existing wounds)
• Type 2 - Group A Streptococcus (previously healthy)

Question 9

What antibiotic therapy is used for necrotising fasciitis? (Fasciitis Can Get Mega Bad)

Answer 9

• Flucloxacillin
• Clindamycin
• Gentamicin
• Metronidazole
• Benzylpenicillin

NB - Also requires urgent surgical debridement (do not delay contacting surgeon if necrotising fasciitis suspected) and haemodynamic support

Question 10

What are the clinical features of HSV and how is it treated?

Answer 10

• Primary infection asymptomatic in 60%
• Type 1 - stomatitis ‘cold sore’
• Type 2 - genital herpes
• Vesicular, may be painful
• Other symptoms include dysuria (in women), lymphadenopathy, genital ulcers, oral ulcers and tingling sensations.
• Recurrent (virus latent in sensory nerve ganglia)
• Blood or vesicle fluid for PCR to diagnose
• Treat with acyclovir

Question 11

What are the clinical features of VZV and how is it treated?

Answer 11

• Chickenpox is self-limiting, highly infectious, diagnosed by PCR and can cause congenital abnormalities in pregnancy and pneumonitis in adults
• Shingles is reactivation of dormant VZV (dorsal root ganglia) with a dermatomal distribution and is treated with acyclovir in high risk patients (immunocompromised, disseminated)
• Supportive care
• Treat at risk adults (pregnant, immunocompromised, pneumonitis) with Aciclovir PO/IV

Question 12

What organisms are common in bite injuries and how are they treated?

Answer 12

• Staphylococci, streptococci and anaerobic organisms common
• First line co-amoxiclav
• Second line doxycycline and metronidazole
• Surgical debridement may be required

Question 13

Cause of cellulitis

Answer 13

• β-haemolytic streptococci (Gp A Strep most common) and S. aureus

Question 14

Features of cellulitis

Answer 14

• Signs/symptoms include skin discomfort, macular erythema with indistinct borders of the skin, disruption of cutaneous barrier, raised erythema with clearly demarcated margins and Hx of diabetes.
• Risk factors include Hx of cellulitis, ulcers/wounds, dermatosis, tinea pedis interdigitalis, lymphoedema and venous.