Necrotizing Soft Tissue Infection

Definitions of Skin/Soft Tissue Infections

  • Cellulitis (see Cellulitis, [[Cellulitis]]): skin infection of deeper dermis and subcutaneous fat (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
  • Erysipelas (see Erysipelas, [[Erysipelas]]): skin infection of upper dermis and superficial lymphatics (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
  • Impetigo (see Impetigo, [[Impetigo]]): infection of superficial layers of the epidermis
  • Necrotizing Soft Tissue Infection: all of these are characterized by fulminant tissue destruction, systemic toxicity, and high mortality rates
    • Necrotizing Cellulitis
      • Meleney’s Synergistic Gangrene
      • Clostridial Anaerobic Necrotizing Cellulitis
      • Non-Clostridial Anaerobic Necrotizing Cellulitis
    • Necrotizing Fasciitis: deep-seated infection of subcutaneous tissue (involving fascia and fat), which may spare the skin
      • Type I (Mixed Aerobic and Anaerobic Infection)
      • Type (Monomicrobial Infection)
    • Necrotizing Myositis (Spontaneous Gangrenous Myositis): xxx
  • Clostridial Myonecrosis (Gas Gangrene) (see Clostridial Myonecrosis, [[Clostridial Myonecrosis]]): life-threatening muscle infection which develops either contiguously from a site of trauma or via hematogenous spread from the gastrointestinal tract to the muscle
  • Furuncle (Boil) (see Skin Abscess, [[Skin Abscess]]: infection of hair follicle where purulent material extends through the dermis into the subcutaneous tissue, forming a small abscess
  • Carbuncle (see Skin Abscess, [[Skin Abscess]]: coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from multiple follicles
  • Skin Abscess (see Skin Abscess, [[Skin Abscess]]): collection of pus within dermis and deeper skin tissues

SKIN INFECTIONS

History

  • Civil War: first description of necrotizing fasciitis by the Confederate Army surgeon, Joseph Jones
  • 1883: Fournier described necrotizing fasciitis in the perineal and genital region
  • 1952: Wilson first used the term “necrotizing fasciitis”

Diagnosis

Laboratory Risk Indicator for Necrotizing Soft Tissue Infection (LRINEC)

  • C-Reactive Protein (CRP) (mg/L)
    • CRP < 150 -> 0 points
    • CRP ≥ 150 -> 4 points
  • WBC
    • WBC < 15 -> 0 points
    • WBC 15-25 -> 1 point
    • WBC >25 -> 2 points
  • Hemoglobin (g/dL)
    • Hb >13.6 -> 0 points
    • Hb 11-13.5 -> 1 points
    • Hb < 10.9 -> 2 points
  • Sodium (mmol/L)
    • Na ≥ 135 -> 0 points
    • Na < 135 -> 2 points
  • Creatinine (mg/dL)
    • Cr ≤ 1.6 -> 0 points
    • Cr >1.6 -> 2 points
  • Glucose (mg/dL)
    • Glc ≤ 180 -> 0 points
    • Glc >180 -> 1 point
  • LRINEC Score -> Probability of Necrotizing Fasciitis
    • Low Risk: <5 points -> <50% probability of necrotizing fasciitis
    • Intermediate Risk: 6-7 points -> 50-75% probability of necrotizing fasciitis
    • High Risk: >8 points -> >75% probability of necrotizing fasciitis

Complete Blood Count (CBC) (see Complete Blood Count, [[Complete Blood Count]])

X-Rays

  • May Reveal Gas in Soft Tissues: although these are of limited utility in cases where gas is unlikely to be found (ie: those due to Strep and MRSA) and may delay the necessary surgical management

CT

  • Useful to Image Soft Tissues

MRI

  • Useful to Differentiate Fasciitis from Cellulitis
    • Gas in deep tissues is more common with Clostridium and mixed aerobic-anerobic cases (but is unusual in Strep and MRSA-associated cases)

Ultrasound with Aspiration of Perifascial Fluid Collections

  • May Be Useful
    • “Dishwater” appearance of fluid

Finger Test

  • Procedure: 2 cm incision down to deep fascia (with local anesthesia)
    • Lack of bleeding from incision or “dishwater” fluid expressed -> suggest necrotizing fasciitis
    • If the tissues at level of the deep fascia dissect with minimal resistance, the finger test is positive -> suggests necrotizing fasciitis

Tissue Biopsy with Rapid Frozen Section Analysis

  • May Demonstrate Obliterative Vasculitis of Subcutaneous Vessels, Acute Inflammation, and Subcutaneous Tissue Necrosis

Clinical Pattern-Necrotizing Cellulitis

Meleney’s Synergistic Gangrene

  • Epidemiology
    • Rare
    • Occurs in Postoperative Patients
  • Microbiology
    • Combined Staphylococcus Aureus + Microaerophilic Streptococci (see Staphylococcus Aureus, [[Staphylococcus Aureus]] and Streptococcus, [[Streptococcus]]): involves a synergistic interaction between these organisms
  • Physiology
    • Confined to the Superficial Fascia
  • Clinical
    • Slowly Expanding Indolent Ulceration Confined to Superficial Fascia

Clostridial Anaerobic Necrotizing Cellulitis

  • Epidemiology
    • XXXX
  • Microbiology
  • Physiology
    • Portal of Entry
      • Spread of Infection from Bowel to Perineum/Abdominal Wall/Lower Extremities
      • Surgical Contamination
      • Trauma
  • Clinical
    • Gradual Onset with Subsequent Rapid Spread
    • Pain/Swelling/Systemic Toxicity are Not Prominent Features
      • Milder Clinical Illness Distinguishes this from True Gas Gangrene
    • Thin, Dark, Foul-Smelling Wound Drainage: may contain fat globules
    • Tissue Gas Formation (see Skin Crepitus, [[Skin Crepitus]])
      • Sparing of Fascia and Deep Muscle
  • Treatment
    • Surgical Exploration/Debridement is Required to Distinguish Anaerobic Cellulitis from Fasciitis and Myonecrosis

Non-Clostridial Anaerobic Necrotizing Cellulitis

  • Epidemiology
  • Microbiology: non-spore forming anaerobic bacteria with/without facultative organisms
    • Non-Spore Forming Anaerobic Bacteria
    • Facultative Bacteria
      • Coliforms/Gram-Negative Rods
      • Staphylococcus (see Staphylococcus, [[Staphylococcus]])
      • Streptococcus (see Streptococcus, [[Streptococcus]])
  • Clinical
    • Gradual Onset with Subsequent Rapid Spread
    • Pain/Swelling/Systemic Toxicity are Not Prominent Features
      • Milder Clinical Illness Distinguishes this from True Gas Gangrene
    • Thin, Dark, Foul-Smelling Wound Drainage: may contain fat globules
    • Tissue Gas Formation (see Skin Crepitus, [[Skin Crepitus]])
      • Sparing of Fascia and Deep Muscle

Clinical Pattern-Necrotizing Fasciitis

Type I Necrotizing Fasciitis

Epidemiology

  • Type I is the Most Common Type of Necrotizing Fasciitis
  • Risk Factors

    Clinical Scenarios

    • Cervical Necrotizing Fasciitis of the Neck
      • Microbiology
        • Most Cases are Due to Mixed Aerobic and Anaerobic Infection
      • Portal of Entry
        • Breach in the Oropharyngeal Mucous Membrane Due to Surgery, Instrumentation, or Odontogenic Infection
      • Clinical
        • Fasciitis May Spread to Face, Lower Neck, or Mediastinum
    • Fournier’s Gangrene (see Fournier’s Gangrene , [[Fourniers Gangrene]])
      • Sex
        • Most Common in Older Males
        • Female Cases May Occur in the Setting of Diabetes Mellitus
      • Risk Factors
      • Physiology
        • Breach in Gastrointestinal/Genitourinary Tract or Labia: by diverticulum, malignancy, hemorrhoid, anal fissure/perianal abscess, Bartholin abscess, episiotomy, , vulvovaginal infection, decubitus ulcer, or urethral tear
        • Once Infection Reaches the Deep Fascia of Perineum, Rapid Spread Along Fascial Planes, Through Venous Channels and Lymphatics to Involve the Anterior Abdominal Wall/Gluteal Muscles/Scrotum/Penis
      • Clinical
        • Fever (see Fever, [[Fever]]): early finding
        • Abrupt Onset of Severe Pain Over Skin and Underlying Muscle: sensitive, early finding that may precede development of fever (Chest, 2005) [MEDLINE]
        • Crepitus (see Skin Crepitus, [[Skin Crepitus]]): may occur
        • Penile Edema
        • Scrotal Swelling
        • Vesicular Skin Lesions (see Vesicular-Bullous-Pustular Skin Lesions, [[Vesicular-Bullous-Pustular Skin Lesions]]): may occur
        • Extension into Perineum/Abdominal Wall/Lower Extremities (with skin findings, as noted for other presentations)
        • Myositis (Occurs Concomitantly in 20-40% of Cases): elevated CK
        • Septic Shock/Multiorgan Failure (see Sepsis, [[Sepsis]])
      • Treatment: early aggressive drainage/debridement (may require cystostomy, colostomy, or orchiectomy)
    • Lower Extremity Necrotizing Fasciitis
      • Epidemiology
        • Most Common Site in Cases Associated with Diabetes Mellitus and Peripheral Arterial Disease
    • Ludwig’s Angina (see Ludwig’s Angina, [[Ludwigs Angina]])
      • Clinical
        • XXXX
    • Surgical Wound Infection
      • Clinical
        • Copious Drainage
        • Dusky, Friable Subcutaneous Tissue with Pale, Devitalized Fascia
    • Neonatal Necrotizing Fasciitis
      • Clinical
        • Usually Associated with Omphalitis (Most Commonly), Balanitis, Mammitis, or Fetal Monitoring
        • Most Commonly Involves Abdomen/Perineum

    Type II Necrotizing Fasciitis

    General Comments

    • Type II Necrotizing Fasciitis is Usually Monomicrobial

    Cervical Necrotizing Fasciitis of the Neck

    • Portal of Entry
      • Breach in the Oropharyngeal Mucous Membrane Due to Surgery, Instrumentation, or Odontogenic Infection
    • Microbiology
    • Clinical
      • Fasciitis May Spread to Face, Lower Neck, or Mediastinum

    Staphylococcal Necrotizing Fasciitis

    • Epidemiology
      • XXX
    • Risk Factors
      • Diabetes Mellitus (DM) (see Diabetes Mellitus, [[Diabetes Mellitus]])
      • Insect Bite
      • Intravenous Drug Abuse (IVDA) with Subcutaneous Injection of Black Tar Heroin (see Intravenous Drug Abuse, [[Intravenous Drug Abuse]])
      • Peripheral Arterial Disease (PAD) (see MEDLINE]
      • Fever (see Fever, [[Fever]]): may be absent early
      • Brawny Edema: may extend beyond the area of erythema
        • Subcutaneous tissues may feel wooden/hardened with loss of feeling of fascial planes and muscle groups
      • Vesicular Skin Lesions: may occur
      • Crepitus (see Skin Crepitus, [[Skin Crepitus]]): may occur
    • Later Findings
      • Dark Red Induration of Skin
      • Bullae Filled with Blue/Purple Fluid
    • Late Findings
      • Friable Bluish/Maroon/Black Skin (due to extensive thrombosis of blood vessels in dermal papillae)
      • Brownish/Gray Skin (due to extension into the deep fascia)
    • Septic Shock/Multiorgan Failure (see Sepsis, [[Sepsis]])

Streptococcal Gangrene

  • Epidemiology
    • Age: can occur in any age group
    • Most Cases are Community-Acquired
    • Most Cases Occur in Patients without Co-Morbid Conditions (in Contrast to Type I Necrotizing Fasciitis Cases)
    • Of the 3.5 Million Cases of Invasive Streptococcus Pyogenes Cases Per Year in th US, Necrotizing Fasciitis Accounts for Approximately 6% of These Cases
    • Incidence: appears to be increasing since 1985
  • Risk Factors
  • Microbiology
    • Streptococcus Pyogenes (Group A Strep) (see Streptococcus Pyogenes, [[Streptococcus Pyogenes]]): most common Streptococcus species associated with necrotizing fasciitis
      • Concomitant Streptococcus Pyogenes and Staphylococcus Infection May Occur in Some Cases
    • Streptococcus Agalactiae (Group B Strep) (see Streptococcus Agalactiae, [[Streptococcus Agalactiae]]): reported cases
  • Physiology
    • Cases with Defined Portal of Entry: 50% of cases
      • Infection Usually Enters Through Penetrating Trauma or Cutaneous Site of Infection
      • Early Findings: signs of superficial skin infection
      • Later Findings: purple (violaceous) bullae, skin sloughing, etc
      • Once Infection Reaches the Deep Fascia, it Rapidly Spreads Along Fascial Planes, Through Venous Channels and Lymphatics
    • Cases with No Defined Portal of Entry: 50% of cases
      • Asymptomatic/Symptomatic Pharyngitis Likely Results in Subsequent Hematogenous Dissemination to a Site of Non-Penetrating Minor Trauma (Such as a Bruise or Muscle Strain)
      • Early Findings: severe pain, fever (without signs of superficial skin infection)
      • Later Findings: purple (violaceous) bullae, skin sloughing, etc
  • Clinical
    • Approximately 66% of Cases Occur in the Lower Extremities
    • Early Findings
      • Severe Pain Over Skin and Underlying Muscle: sensitive, early finding that may precede development of fever and other constitutional symptoms [MEDLINE]
      • Crepitus (see Skin Crepitus, [[Skin Crepitus]]): may occur
      • Fever: may be absent early
      • Brawny Edema: may extend beyond the area of erythema
        • Subcutaneous tissues may feel wooden/hardened with loss of feeling of fascial planes and muscle groups
      • Vesicular Skin Lesions: may occur
    • Later Findings
      • Dark Red Induration of Skin
      • Bullae Filled with Blue/Purple Fluid
    • Late Findings
      • Friable Bluish/Maroon/Black Skin (due to extensive thrombosis of blood vessels in dermal papillae)
      • Brownish/Gray Skin (due to extension into the deep fascia)
    • Septic Shock/Multiorgan Failure (see Sepsis, [[Sepsis]])

Anaerobic Streptococcus (Peptostreptococcus) (see Peptostreptococcus, [[Peptostreptococcus]])

  • Epidemiology
    • XXXX

Aeromonas Hydrophila-Associated Necrotizing Fasciitis (see Aeromonas Hydrophila, [[Aeromonas Hydrophila]])

  • Epidemiology
    • Necrotizing Soft Tissue Infection is Associated with Traumatic Injuries in Freshwater
  • Clinical
    • XXXX

Clostridium Novyii-Associated Necrotizing Fasciitis (see Clostridium Novyii, [[Clostridium Novyii]])

  • Epidemiology
    • XXXX
  • Risk Factor
    • Intravenous Drug Abuse (IVDA) with Subcutaneous Injection of Black Tar Heroin (see Intravenous Drug Abuse, [[Intravenous Drug Abuse]])
  • Portal of Entry
    • Breach of Skin/Mucosa
  • Clinical
    • Gas Gangrene

Clostridium Sordellii-Associated Necrotizing Fasciitis (see Clostridium Sordellii, [[Clostridium Sordellii]]

  • Epidemiology
    • XXXX
  • Risk Factor
    • Intravenous Drug Abuse (IVDA) with Subcutaneous Injection of Black Tar Heroin (see Intravenous Drug Abuse, [[Intravenous Drug Abuse]])
  • Portal of Entry
    • Breach of Skin/Mucosa
  • Clinical
    • Necrotizing Fasciitis

Vibrio Vulnificus-Associated Necrotizing Fasciitis (see Vibrio Vulnificus, [[Vibrio Vulnificus]])

  • Epidemiology
    • Necrotizing Soft Tissue Infection is Associated with Traumatic Injuries in Seawater
    • Necrotizing Soft Tissue Infection in Patients with Cirrhosis is Associated with Ingestion of Contaminated Oysters
  • Portal of Entry
    • Breach of Skin/Mucosa
  • Clinical
    • XXXX

Synergistic Necrotizing Cellulitis

  • Epidemiology
  • Clinical
    • Variant of Necrotizing Fasciitis Which Involves the Skin/Muscle/Fat/Fascia
    • Usually Involves the Lower Extremities or Perineum

Clinical Pattern-Necrotizing Myositis (Spontaneous Gangrenous Myositis)

Epidemiology

  • xxxx
    • XXXX

Microbiology

  • xxx

Clinical

  • xxxx

Gallery

Example of Streptococcus Pyogenes Necrotizing Cellulitis

  • 62 y/o Female with Left Forearm Cellulitis After Superficial Wound

Example of Type I Necrotizing Fasciitis

  • 36 y/o Diabetic Caucasian Male (with HbA1C 13%) Who Presented with Ulcerating Left Foot Skin Lesions
    • Patient Underwent Immediate Surgical Incision and Drainage of the Left Foot/Distal Left Leg and Left Great Toe Amputation
    • 12 hrs Later, He Developed Progressive Gangrene Adjacent to the Surgical Field (Picture Below), Requiring Repeat Surgical Debridement with Left Below the Knee Amputation
    • Blood Cultures were Positive for Streptococcus Agalactiae (Group B Streptococcus)
    • Wound Cultures were Positive for Escherchia Coli + Streptococcus Agalactiae (Group B Streptococcus)*

NEC FASC

Treatment

Antibiotics

  • Clindamycin (see Clindamycin, [[Clindamycin]])
    • Unlike penicillin, the efficacy of clindamycin is not affected by the inoculum size or stage of bacterial growth
    • Clindamycin suppresses bacterial toxin synthesis
    • Subinhibitory concentrations of clindamycin facilitate Strep Pyogenes phagocytosis
    • Clindamycin decreases the synthesis of penicillin-binding protein, which, in addition to being a target for penicillin, is also an enzyme involved in cell wall synthesis and degradation
    • Clindamycin has a longer postantibiotic effect than β-lactams (such as penicillin)
    • Clindamycin suppresses LPS-induced mononuclear synthesis of tumor necrosis factor-α
  • Vancomycin (see Vancomycin, [[Vancomycin]]): or comparable agent, to cover for possible MRSA
  • Gram-Negative Coverage: also useful

Intravenous Immunoglobulin (IVIG) (see Intravenous Immunoglobulin, [[Intravenous Immunoglobulin]])

  • Reported in the Treatment of Streptococcal Toxic Shock Syndrome (see Streptococcal Toxic Shock Syndrome, [[Streptococcal Toxic Shock Syndrome]]): may have a role in Streptococcus-associated necrotizing faasciitis cases (although this is not an FDA-approved indication)

Prompt Surgical Debridement Down to Fascia with Wide Excision

  • Early surgical intervention has been demonstrated to improve mortality and decrease tissue loss (amputation, etc).
    • Delayed surgical intervention is associated with increased risk of death [MEDLINE]
      • Average latency from admission to surgery in survivors: 25 hrs
      • Average latency from admission to surgery in non-survivors: 90 hrs

Hyperbaric Oxygen (HBO) (see Hyperbaric Oxygen, [[Hyperbaric Oxygen]])

  • Unclear Benefit in Necrotizing Fasciitis

Treatment of Septic Shock (see Sepsis, [[Sepsis]])

  • Standard Measures

Prognosis

  • Death: may occur if necrotizing fasciitis is not promptly recognized and treated

References

  • Determinants of mortality for necrotizing soft-tissue infections. Ann Surg. May 1995;221(5):558-63 [MEDLINE]
  • Necrotizing fasciitis. Chest. Jul 1996;110:219-29 [MEDLINE]
  • The changing spectrum. Dermatol Clin. Apr 1997;15(2):213-20 [MEDLINE]
  • Group B streptococcal necrotizing fasciitis and streptococcal toxic shock-like syndrome in adults. Arch Intern Med. 1998 Aug 10-24;158(15):1704-8 [MEDLINE]
  • A 46-year-old man with excruciating shoulder pain. Chest. Mar 2005;127(3):1039-44 [MEDLINE]
  • Necrotizing soft-tissue infection: diagnosis and management. Clin Infect Dis. 2007;44(5):705 [MEDLINE]
  • Group B streptococcal necrotizing fasciitis from a decubitus ulcer. Int J Emerg Med. 2010 Dec; 3(4): 519–520 [MEDLINE]
  • Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2014 Jul 15;59(2):e10-52. doi: 10.1093/cid/ciu444 [MEDLINE]
  • Necrotising soft tissue infection in a UK metropolitan population. Ann R Coll Surg Engl. 2015 Jan;97(1):46-51. doi: 10.1308/003588414X14055925058553 [MEDLINE]