Necrotising fasciitis

Necrotising fasciitis (NF):

It is an infection of the subcutaneous tissue/fat and fascia of the skin. It spreads rapidly along the fascial plane. Muscles are less commonly affected/ affected later in the disease due to better blood supply.

Classification

Types	Organism	Note
Type 1 – polymicrobial/synergistic	Aerobic and anaerobic bacteria	Often derived from gut/bowel
Type 2 – monomicrobial	Group A Streptococcus (Strep pyogenes), occasionally Staph aureus (especially neonates);	Commonly skin or throat derived.
Type 3	Vibrio spp mainly; Other organism – Pasteurella multocida, Haemophilus influenzae , Klebsiella spp. and Aeromonas spp.	Common in Asia, associated with seafood/seawater
Type 4	Fungal (Candida in immunocompromised or zygomycetes in immunocompetent patients)

Type 1 is the commonest (up to 80% of cases).
Type 4 has the highest mortality.

Some authorities classify necrotising fasciitis as only two types –
Type 1 – polymicrobial.
Type 2 – monomicrobial (NF caused by Vibrio, fungus etc., falls into this category).

Mortality

Approx 20%. It is a surgical emergency

Common sites

Perineum and lower extremities (commonest)
Surgical site,
Upper extremities,
Abdomen,
Mouth
Face

Predisposing factors

Trauma – including surgery
Burns
Skin and soft tissue infection
Immunosuppression
Obesity/malnutrition
Alcoholism
Peripheral vascular disease
Intravenous drug abuse and
Diabetes mellitus
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Diabetes is the most common preexisting medical condition.
In children, it is usually associated with recent varicella-zoster.

Presentation

• Common signs/symptoms are – swelling (75%), pain (72.9%), and erythema (66.3%) [Diab, BMJ 2020].
• The skin changes often do not reflect the extent of the damage.
  Pain could be out of proportion to skin changes.
  Anaesthesia over the infected area also could be present.
• One-fifth of patients have influenza-like symptoms characterised by fever and myalgia.
• Inflammatory markers (WCC, CRP) could be raised along with creatine kinase and creatinine.
• Patients may deteriorate rapidly, developing signs of sepsis. In later stages NFcould present with visible bruising, bullae and cutaneous necrosis.

Management

• It is a surgical emergency – an immediate surgical referral.
• Debridement.
• Haemodynamic support.
• Critical care support.
• Broad-spectrum empirical antibiotic.

Antibiotics should cover both type 1 and type 2 pathogens.

1. A broad-spectrum antibiotic with gram-negative and gram-positive cover –
   Pip-tazobactam or a carbapenem (e.g. meropenem).
2. An antibiotic to inhibit group A Streptococcus toxin production –
   Clindamycin or Linezolid
3. An antibiotic to cover MRSA (according to the local microbiology or presence of risk factors for MRSA) –
   Vancomycin or daptomycin, or linezolid.

• Isolation of the patient until group A Streptococcus is excluded as a pathogen or, if isolated, managed accordingly.
• Infection control.
• If group A Streptococcus is isolated – inform public health.