What are the most common skin infections in practice and their treatments?

Most Common Skin Infections in Practice and Their Treatments

The most common skin infections in clinical practice are impetigo, cellulitis, erysipelas, and folliculitis (including furuncles and carbuncles), with Staphylococcus aureus and Streptococcus pyogenes being the predominant causative pathogens. 1, 2

Common Skin Infections

Impetigo

• Caused by S. aureus and/or S. pyogenes 1
• Presents as honey-colored crusted lesions (non-bullous) or thin-roofed vesicopustules (bullous) 1
• Treatment:
  • Localized: Topical mupirocin or retapamulin twice daily for 5 days (strong recommendation) 1
  • Widespread: Oral antibiotics active against both S. aureus and S. pyogenes for 7 days 1
    • First-line: Dicloxacillin or cephalexin 1, 3
    • For MRSA or penicillin allergy: Doxycycline, clindamycin, or sulfamethoxazole-trimethoprim (SMX-TMP) 1

Cellulitis and Erysipelas

• Cellulitis: Infection of dermis and subcutaneous tissue with poorly demarcated borders, usually caused by streptococci or staphylococci 1
• Erysipelas: Superficial form of cellulitis with well-demarcated borders, typically caused by streptococci 1, 4
• Treatment:
  • For erysipelas: Penicillin (oral or parenteral depending on severity) is the treatment of choice 1
  • For cellulitis: Penicillinase-resistant semisynthetic penicillin or first-generation cephalosporin 1
    • Options include penicillin, amoxicillin, amoxicillin-clavulanate, dicloxacillin, cephalexin, or clindamycin 1
    • Duration: 5-day course is as effective as 10-day course if clinical improvement occurs by day 5 1
    • MRSA coverage is usually unnecessary for typical cellulitis but may be prudent in cases with purulent drainage, penetrating trauma, or concurrent MRSA infection elsewhere 1

Folliculitis, Furuncles, and Carbuncles

• Folliculitis: Inflammation of hair follicles, commonly caused by S. aureus 2, 4
• Furuncles (boils): Deeper infection of hair follicle 4
• Carbuncles: Coalescence of multiple furuncles 4
• Treatment:
  • Mild folliculitis: Topical antibiotics 2
  • More severe or extensive: Systemic antibiotics active against S. aureus 2, 5
  • Furuncles/carbuncles: Incision and drainage is primary treatment, with antibiotics if extensive surrounding cellulitis or systemic symptoms 1

Antibiotic Selection

First-line Antibiotics

• For streptococcal infections (erysipelas): Penicillin 1
• For staphylococcal or mixed infections: Beta-lactam antibiotics 1
  • Dicloxacillin, cephalexin, amoxicillin-clavulanate 3, 2
• For penicillin-allergic patients: Clindamycin, macrolides, or (for MRSA) SMX-TMP 1, 6

MRSA Considerations

• MRSA is an unusual cause of typical cellulitis but should be considered in:
  • Purulent infections 1
  • Penetrating trauma, especially from illicit drug use 1
  • Areas with high MRSA prevalence 1
  • Treatment failure with beta-lactams 1
• Options for MRSA treatment:
  • Oral: Doxycycline, clindamycin, or SMX-TMP 1
  • IV (for severe infections): Vancomycin, daptomycin, linezolid, or telavancin 1

Special Considerations

Duration of Therapy

• Uncomplicated cellulitis: 5 days if clinical improvement occurs 1
• More severe infections: Typically 7-14 days 1, 2

Adjunctive Measures

• Elevation of affected area to promote gravity drainage of edema 1
• Treatment of predisposing conditions (tinea pedis, venous eczema) 1
• Systemic corticosteroids may be considered in nondiabetic adults with cellulitis (weak recommendation) 1

Recurrent Infections

• Annual recurrence rates of 8-20% for cellulitis, especially in the legs 1
• Risk factors: Edema (especially lymphedema), venous insufficiency, prior trauma, tinea pedis, obesity, tobacco use 1
• Addressing these factors may decrease recurrence frequency 1

Pitfalls and Caveats

• Blood cultures are unnecessary for typical cellulitis but should be obtained for patients with malignancy, severe systemic features, or unusual predisposing factors 1
• S. aureus has high resistance rates to penicillin (89.5%) but remains largely sensitive to cloxacillin, cephalexin, and cotrimoxazole 5
• The combination of ampicillin and cloxacillin has limited utility except for cellulitis and infected eczemas 5
• Secondary pyodermas (infected ulcers, infected eczemas) have higher rates of gram-negative organisms and methicillin-resistant strains, often requiring broader coverage 5