Definitions

• 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 Fasciitis (see Necrotizing Fasciitis, Necrotizing Fasciitis): deep-seated infection of subcutaneous tissue (involving fascia and fat), which may spare the skin
• Furuncle (Boil): infection of hair follicle where purulent material extends through the dermis into the subcutaneous tissue, forming a small abscess
• Carbuncle: coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from multiple follicles
• Skin Abscess: collection of pus within dermis and deeper skin tissues

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Predisposing Factors

• Diabetes Mellitus (see Diabetes Mellitus, Diabetes Mellitus)
• Immunodeficiency
  • Chronic Granulomatous Disease (CGD) (see Chronic Granulomatous Disease, Chronic Granulomatous Disease)
• Immunosuppression
• Intravenous Drug Abuse (IVDA) (see Intravenous Drug Abuse, Intravenous Drug Abuse): particularly “skin popping”
• Nasal Carriage of Staphylococcus Aureus (see Staphylococcus Aureus, Staphylococcus Aureus): may be the only risk factor present in a normal patient who develops skin abscess
• Skin Barrier Breach

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Microbiology

• General Comments
  • Approximately 7% of Cases are Polymicrobial
• Staphylococcus Aureus (see Staphylococcus Aureus, Staphylococcus Aureus: most common etiology
  • Methicillin-Resistant Staphylococcus Aureus (MRSA)
• Staphylococcus Epidermidis (see Staphylococcus Epidermidis, Staphylococcus Epidermidis
• Streptococcus (see Streptococcus, Streptococcus)
• Nocardiosis (Disseminated) (see Nocardiosis, Nocardiosis): subcutaneous skin abscesses with/without sinus tracts

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Diagnosis

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

• Findings
  • Leukocytosis (see Leukocytosis, Leukocytosis)

Blood Culture (see Blood Culture, Blood Culture)

• xxxx

Ultrasound

• Useful to Localize a Defined Pocket of Abscess Fluid
  • Studies Indicate that MRSA Can Be Suspected Based on Ultrasound Characteristics of a Skin Abscess (Acad Emerg Med, 2014) [MEDLINE]

Culture of Abscess Drainage Material

• Indicated

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Clinical Manifestations

Dermatologic Manifestations

Painful/Tender, Erythematous Fluctuant Skin Nodule

• May have central pustule
• May be surrounded by a rim of erythematous edema

Other Manifestations

Sepsis (see Sepsis, Sepsis)

• xxx

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Treatment

Small Furuncle

• Warm Compress: when used alone, may promote drainage

Skin Abscess or Medium-Large Furuncle/Carbuncle

• Incision and Drainage (I+D)
• Indications for Concomitant Antibiotic Therapy (Based on Infectious Disease Society America/IDSA guidelines)
  • Abscess Present in Difficult to Drain Area: face, hand, genitals
  • Associated Septic Phlebitis
  • Comorbid Disease
  • Extreme of Age
  • Immunosuppression
  • Lack of Clinical Response to Incision and Drainage (I+D) Alone
  • Rapid Progression with Associated Cellulitis
  • Severe or Extensive Disease with Multiple Sites of Infection
  • Systemic Toxicity
• Clinical Efficacy
  • Trial of Sulfamethoxazole-Trimethoprim for Skin Abscess (NEJM, 2016) MEDLINE]: in skin abscesses at least 2 cm in size which were drained, sulfamethazole-trimethoprim increased cure rate at 7 and 14 days
    • Wound Cultures were Positive for MRSA in 45% of Cases
    • Abscess Size of At Least 2 cm is Considered a Useful Threshold Regarding Deciding on Antibiotic Use as Adjunctive Therapy for Skin Abscess

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References

• 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]
• Management of Skin Abscesses in the Era of Methicillin-Resistant Staphylococcus aureus. N Engl J Med 2014; 370:1039-1047March 13, 2014DOI: 10.1056/NEJMra1212788 [MEDLINE]
• The Massachusetts abscess rule: a clinical decision rule using ultrasound to identify methicillin-resistant Staphylococcus aureus in skin abscesses. Acad Emerg Med. 2014 May;21(5):558-67. doi: 10.1111/acem.12379 [MEDLINE]
• Trimethoprim-Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess. N Engl J Med. 2016;374(9):823 [MEDLINE]