Fournier gangrene – synergistic gangrene of the genitalia, usually following genital trauma (eg postpartum) or spread from a perianal, retroperitoneal or urinary tract infection; unfortunately has a high death rate ranging from 15% to 50%
Necrotising infection of the head and neck – generally polymicrobial and can occur in the setting of odontogenic infection or following oropharyngeal surgery or trauma
Definitions
Type 1: Polymyocrobial
Causes include: Staphylococcus aureus, Haemophilus, Vibrio and several other aerobic and anaerobic strains (Escherichia coli, Bacteroides fragilis)
Usually seen in older people or in patients affected by diabetes mellitus or other conditions
Type 2: Haemolytic group A streptococcus and/or staphylococci including MRSA
Sensationalised in the media as flesh-eating disease
Affects all age groups and healthy people are also prone to infection (almost half of cases)
Type 3: Gas gangrene
Usually follows significant injury or surgery typically with associated vascular compromise and results in gas under the skin
People who inject “black tar” heroin subcutaneously can also be infected with clostridia
Risk Factors
Streptococcal necrotising fasciitis can occur in young and previously health individuals
Precipitating factors:
An opening in the skin that allows bacteria to enter the body such as minor injury (e.g. small cut, graze, pinprick, injection) or large wound (eg, laparoscopy, sclerotherapy, endoscopic gastrostomy, thoracostomy, Caesarean section, hysterectomy); but often no point of entry can be found
Cervicofacial necrotising fasciitis can follow mandibular fracture or dental infection
Direct contact with a person who is carrying the bacteria or the bacteria is already present elsewhere on the person
In children, type II necrotising fasciitis may complicate chickenpox
S. pyogenes necrotising fasciitis typically involves the limb and is associated with nonpenetrating trauma or any injury that breaks the skin
Risk factors:
NSAIDs
Advanced age
Diabetes mellitus
Immune suppression
Obesity
Drug abuse
Severe chronic
illness
Malignancy
Clinical Features
Consider necrotising infection in patients who are critically ill with a skin and soft tissue infection
Most common site of infection is lower leg but may also affect upper limb, perineum, buttocks, trunk, head and neck
Symptoms appear usually within 24 hours of a minor injury
Diagnosis of necrotising skin and soft tissue infections is difficult but clinical features include:
Constant severe pain, even if skin inflammation is initially limited
Bullae
Skin necrosis or bruising
Hard (‘wooden’) subcutaneous tissue that is painful on palpation
Oedema beyond the margin of erythema
Cutaneous anaesthesia
Gas in the soft tissues (detected by palpation with skin or soft tissue crepitus or imaging)
Systemic features, including fever, leucocytosis, elevated C-reactive protein (CRP), delirium or acute kidney impairment
Rapidly spreading infection
Penetrating and crush injuries often lead to necrotising skin and soft tissue infections
Clostridial and streptococcal infections as a result of traumatic or surgical wound usually manifest quickly compared to necrotising fasciitis due to other organisms
Necrotic tissue/pus- oozes out of the fascial planes
Dishwater-coloured fluid seeps out of the skin
Typically, necrotising fasciitis does not bleed
Diagnosis
History and exam is important in the diagnosis
A positive finger test is highly pathognomic for necrotising fasciitis ⇒ A 2–cm vertical incision is made in the affected skin and an index finger is pushed into the tissue; the test is positive if the finger passes through the subcutaneous tissue without resistance
Management
Mainstay of management is surgical removal of devitalised tissue and urgent antibiotic therapy
Empirical therapy for necrotising skin and soft tissue infection not associated with water exposure use:
Meropenem IV, vancomycin IV and clindamycin IV
Meropenem can be replaced with tazocin if there is low suspicion of multidrug-resistant gram negative infection or meropenem not immediately available
Empirical therapy for necrotising skin and soft tissue infection associated with water exposure use:
Meropenem IV, vancomycin IV, ciprofloxacin IV and clindamycin IV
Where S. pyogenes is suspected, intravenous immunoglobulin (IVIg) as a single dose no later than 72 hours after symptom onset (can be given as multiple doses if not possible to give as single dose)
Modify therapy based on Gram stain, culture and susceptibility:
S. pyogenes ⇒ benzylpenicillin/cefazolin IV, clindamycin IV and IVIG ⇒ step down to oral amoxicillin
Clostridium species ⇒ benzylpenicillin/metronidazole IV and clindamycin
MRSA ⇒ vancomycin and clindamycin
Switch to oral antibiotic therapy when further debridement is no longer necessary, there has been clinical improvement, and the patient has been afebrile for 48 to 72 hours
Sources
eTG Complete: Necrotising skin and soft tissue infections