What is the treatment for a skin infection?

Treatment of Skin Infections

For most skin infections, treatment should include an antibiotic active against streptococci and staphylococci, with specific regimens determined by infection severity, suspected pathogens, and patient factors. 1

Classification and Diagnosis

• Skin infections range from superficial to deep, with varying severity from mild to life-threatening 1
• Differential diagnosis should include bacterial, fungal, viral, and parasitic agents 1
• Biopsy or aspiration of lesions for histological and microbiological evaluation should be implemented as an early diagnostic step, especially in complex or severe cases 1
• Blood cultures should be obtained in patients with systemic symptoms (fever, tachycardia, hypotension) 1

Treatment Approach Based on Infection Type

Uncomplicated Cellulitis/Erysipelas

• For typical cellulitis without purulence, use antibiotics active against streptococci 1
• First-line oral options include:
  • Penicillin, amoxicillin, amoxicillin-clavulanate, dicloxacillin, or cephalexin 1
  • A 5-day course is as effective as a 10-day course if clinical improvement occurs 1
• Elevate the affected area to promote drainage of edema and inflammatory substances 1
• Address predisposing conditions such as tinea pedis, trauma, or venous eczema 1

MRSA Consideration

• MRSA is an unusual cause of typical cellulitis but should be considered with:
  • Penetrating trauma, especially from illicit drug use
  • Purulent drainage
  • Concurrent evidence of MRSA infection elsewhere 1
• If MRSA coverage is needed, options include:
  • Intravenous: vancomycin, daptomycin, linezolid, or telavancin
  • Oral: doxycycline, clindamycin, or trimethoprim-sulfamethoxazole (SMX-TMP) 1
• Note: SMX-TMP should not be used as a single agent for initial cellulitis treatment due to possible group A Streptococcus resistance 1

Skin Abscesses

• Primary treatment is incision and drainage 1
• Culture the wound to identify causative agent and antimicrobial susceptibility 1
• Empirical antibiotic coverage should be guided by local MRSA prevalence 1
• For methicillin-susceptible S. aureus, use oral penicillinase-resistant β-lactams (first or second-generation cephalosporins) 1
• For MRSA or penicillin allergy, use trimethoprim-sulfamethoxazole, doxycycline, or clindamycin for susceptible isolates 1

Complex/Severe Infections

• For severe infections or those progressing despite empirical therapy:
  • Base treatment on Gram stain, culture, and susceptibility results 1
  • For suspected MRSA, use agents such as vancomycin, linezolid, or daptomycin 1
  • Consider broader coverage for complex abscesses (perianal, perirectal, injection sites) with antibiotics effective against Gram-positive, Gram-negative, and anaerobic bacteria 1

Special Considerations for Animal/Human Bites

• For animal bites, recommended treatments include:
  • Amoxicillin-clavulanate, ampicillin-sulbactam, or carbapenems 1
  • For penicillin allergies: fluoroquinolones plus metronidazole or moxifloxacin alone 1
• For human bites, which often involve Eikenella corrodens and anaerobes:
  • Amoxicillin-clavulanate, ampicillin-sulbactam, or ertapenem 1
  • For penicillin allergies: fluoroquinolone plus metronidazole or moxifloxacin alone 1

Treatment in Immunocompromised Patients

• Skin infections in immunocompromised patients require aggressive diagnosis and treatment 1
• Obtain biopsy or aspiration of skin lesions for thorough assessment 1
• Empiric antimicrobial therapy should be initiated immediately based on:
  • Underlying disease
  • Primary immune defect
  • Morphology of skin lesions
  • Prior antimicrobial prophylaxis
  • Local resistance patterns 1
• For fungal infections (common in immunocompromised hosts):
  • Aspergillus: voriconazole is first-line treatment 1
  • Mucor/Rhizopus: lipid formulation amphotericin B or posaconazole 1
  • Fusarium: high-dose IV voriconazole or posaconazole 1
• For viral infections (e.g., VZV, HSV), administer acyclovir 1

Prevention and Follow-up

• For recurrent cellulitis, address predisposing factors like edema, venous insufficiency, trauma, and tinea pedis 1
• Tetanus toxoid should be administered to patients without vaccination within 10 years (Tdap preferred if not previously given) 1
• For athletes with skin infections, ensure proper hygiene practices, avoid sharing equipment, and limit exposure to contaminated surfaces 1

Pitfalls and Caveats

• Failure to recognize necrotizing infections can lead to poor outcomes; watch for:
  • Pain disproportionate to physical findings
  • Violaceous bullae
  • Cutaneous hemorrhage
  • Skin sloughing or anesthesia
  • Rapid progression
  • Gas in tissue 1
• Empirical treatment failure may occur due to:
  • Incorrect initial diagnosis
  • Pathogen resistance
  • Development of resistance during treatment
  • Lack of surgical debridement when needed
  • Profound immune deficiency 1
• Terbinafine (for fungal infections) carries risks of hepatotoxicity, taste/smell disturbances, and serious skin reactions; monitor liver function tests before and during treatment 2