What is the treatment for skin infections?

Treatment for Skin Infections

For superficial skin infections like impetigo, erysipelas, and cellulitis, start with oral antibiotics targeting Gram-positive bacteria (beta-lactams or cephalosporins), but add MRSA coverage (trimethoprim-sulfamethoxazole, doxycycline, or clindamycin) if the patient has risk factors for community-acquired MRSA or fails initial therapy within 24-48 hours. 1, 2

Initial Assessment and Risk Stratification

Determine infection severity immediately:

• Mild superficial infections present with localized erythema, warmth, and tenderness without systemic symptoms 1
• Severe infections requiring hospitalization include patients with fever/hypothermia, tachycardia (>100 bpm), hypotension (systolic BP <90 mmHg), elevated creatinine, low bicarbonate, or C-reactive protein >13 mg/L 1
• Red flags for necrotizing infection include pain disproportionate to findings, violaceous bullae, cutaneous hemorrhage, skin sloughing, skin anesthesia, rapid progression, or gas in tissue—these require emergent surgical evaluation 1

Assess MRSA risk factors:

• Previous MRSA infection
• Recent hospitalization or antibiotic use within 30 days
• Long-term care facility residence
• Age >75 years
• Local MRSA prevalence 1, 2

Treatment Algorithm by Infection Type

Superficial Spreading Infections (Impetigo, Erysipelas, Cellulitis)

For mild infections without MRSA risk factors:

• First-line: Oral beta-lactams (amoxicillin), first-generation cephalosporins (cephalexin), or second-generation cephalosporins 1, 2
• Alternative: Macrolides or clindamycin (note: 50% of MRSA strains have clindamycin resistance) 1
• Duration: 5-10 days based on clinical response 2

For patients at risk for CA-MRSA or failing initial therapy:

• Trimethoprim-sulfamethoxazole (TMP-SMX) PLUS a beta-lactam (for streptococcal coverage) 1, 2
• Doxycycline or minocycline PLUS a beta-lactam 1
• Clindamycin alone (if local susceptibility permits) 1, 2
• Linezolid alone 1, 2

Critical pitfall: Never use TMP-SMX alone for initial treatment of nonpurulent cellulitis due to intrinsic resistance of Group A Streptococcus 2

For localized impetigo:

• Topical mupirocin is sufficient for nonbullous, localized cases 1, 2
• Systemic antibiotics for widespread disease or household outbreaks 1

Simple Abscesses and Boils

Primary treatment is incision and drainage—antibiotics are NOT routinely needed 1, 3

Add antibiotics only if:

• Fever or systemic inflammatory response present 1, 3
• Significant surrounding cellulitis 1
• Immunocompromised patient 1
• Incomplete source control 1

When antibiotics are indicated:

• Clindamycin or TMP-SMX for MRSA coverage 1, 3
• Doxycycline (safe in children ≥2 years for <2 weeks duration) 1
• Duration: 5-10 days based on clinical response 3
• Culture abscess drainage to guide therapy 3

Complex Abscesses (Perianal, Perirectal, IV Drug Use Sites)

Require incision and drainage PLUS broad-spectrum antibiotics covering aerobic and anaerobic organisms 1

Empiric antibiotic regimens:

• Piperacillin-tazobactam 3.37g IV every 6-8 hours 1
• Ampicillin-sulbactam 1
• Carbapenem (imipenem 1g IV every 6-8 hours, meropenem 1g IV every 8 hours, or ertapenem 1g IV daily) 1
• Cefotaxime 2g IV every 6 hours PLUS metronidazole 500mg IV every 6 hours 1

Add vancomycin if MRSA suspected 1

For IV drug users:

• Rule out endocarditis if persistent systemic signs 1
• Obtain radiography to exclude foreign bodies 1
• Screen for HIV, HCV, HBV 1

Severe Infections Requiring Hospitalization

For patients with systemic toxicity or progression despite outpatient therapy:

Obtain immediately:

• Blood cultures 1
• Complete blood count with differential 1
• Creatinine, bicarbonate, creatine phosphokinase, C-reactive protein 1
• Gram stain and culture of needle aspiration or punch biopsy 1

Empiric therapy—assume MRSA until proven otherwise:

• Vancomycin 30 mg/kg/day IV in 2 divided doses 1
• Alternative: Linezolid or daptomycin 1
• PLUS broad-spectrum coverage: Piperacillin-tazobactam, carbapenem, or cefotaxime plus metronidazole 1

For necrotizing infections:

• Penicillin 2-4 million units IV every 4-6 hours PLUS clindamycin 600-900mg IV every 8 hours for streptococcal myonecrosis 1
• Clindamycin plus penicillin for clostridial myonecrosis 1
• Emergent surgical debridement is mandatory 1

Bite Wounds (Animal and Human)

Irrigation and debridement are most important—antibiotic prophylaxis NOT generally recommended for clean wounds 1

Antibiotics required for:

• Systemic signs of infection 1
• Immunocompromised patients 1
• Severe cellulitis or deep wounds 1

Antibiotic choice:

• Amoxicillin-clavulanate 500mg PO 4 times daily for 7-10 days (covers Pasteurella, Streptococcus, Staphylococcus, anaerobes) 1
• Alternative: Doxycycline plus ciprofloxacin or ceftriaxone 1

Additional considerations:

• Tetanus toxoid if not vaccinated within 10 years 1
• Rabies post-exposure prophylaxis—consult local health officials 1
• Consider HBV, HCV, HIV post-exposure prophylaxis for human bites 1

Re-evaluation and Treatment Failure

Reassess within 24-48 hours if outpatient therapy initiated 1, 3

Progression despite antibiotics indicates:

• Resistant organism (add MRSA coverage) 1
• Deeper infection than initially recognized 1
• Need for surgical intervention 1

Adjust antibiotics based on culture and susceptibility results 1, 3

Special Populations

Immunocompromised Patients (Neutropenia, Transplant Recipients)

Aggressively pursue diagnosis with aspiration/biopsy of lesions 1

Empiric therapy must cover:

• Resistant bacteria: Vancomycin or linezolid 1
• Fungi: Echinocandin for Candida, voriconazole for Aspergillus 1
• Viruses: IV acyclovir for HSV/VZV 1, 4

Treatment duration: 7-14 days for bacterial infections, 2 weeks after bloodstream clearance for Candida, 6-12 weeks for Aspergillus 1

Pediatric Patients

Dosing adjustments:

• Piperacillin-tazobactam: 60-75 mg/kg/dose every 6 hours IV 1
• Vancomycin: 15 mg/kg/dose every 6 hours IV 1
• Clindamycin: 10-13 mg/kg/dose every 8 hours IV 1
• Doxycycline: Safe for children ≥2 years when used <2 weeks 1

Common Pitfalls to Avoid

• Failing to perform incision and drainage for abscesses—antibiotics alone are insufficient 1, 3
• Using TMP-SMX monotherapy for cellulitis—will miss streptococcal infections 2
• Inadequate drainage leading to treatment failure—ensure complete evacuation of purulent material 3
• Missing necrotizing infection signs—pain out of proportion, bullae, rapid progression require immediate surgery 1
• Insufficient treatment duration—continue until clinical improvement evident, typically 5-10 days 3, 2
• Not obtaining cultures in severe infections—essential for guiding definitive therapy 1, 3