Management of Uncomplicated Superficial Pyoderma (Impetigo)
First-Line Treatment: Topical Therapy
For localized impetigo with few lesions, topical mupirocin or retapamulin is as effective as oral antibiotics and should be the initial treatment choice. 1
Topical Antibiotic Options
Mupirocin 2% ointment applied three times daily achieves clinical improvement in 85-100% of patients within 3-5 days, with over 90% bacterial eradication rates for both S. aureus and S. pyogenes. 2, 3, 4
Retapamulin 1% ointment applied twice daily for 5 days is FDA-approved for patients ≥9 months and demonstrates non-inferior efficacy to oral cephalexin for uncomplicated impetigo (excluding MRSA). 5
Topical therapy offers a superior benefit-to-risk ratio compared to systemic antibiotics, with adverse effects occurring in <3% of patients (primarily mild local reactions). 3, 4
When Topical Therapy Is Appropriate
Use topical treatment for localized disease with few lesions in patients who can apply medication reliably. 1
Topical agents are particularly effective for nonbullous impetigo caused by streptococci or methicillin-susceptible S. aureus. 1
Oral Antibiotic Therapy: When Systemic Treatment Is Needed
Systemic antibiotics are preferred for patients with numerous lesions, in outbreak settings affecting multiple people, or when topical therapy fails, to decrease transmission of infection. 1
First-Line Oral Regimens (Empiric Coverage for Both Streptococci and MSSA)
Cephalexin 500 mg orally every 6 hours for 5 days (pediatric: 25 mg/kg/day in 4 divided doses) provides excellent coverage for both S. aureus and streptococci. 1, 6
Dicloxacillin 250-500 mg orally every 6 hours for 5 days is equally effective for methicillin-susceptible isolates. 1, 6
Treatment duration is 5 days if clinical improvement occurs; extend only if warmth, tenderness, or erythema have not improved within this timeframe. 7
When Streptococci Alone Are Identified
- Penicillin is the drug of choice when cultures yield streptococci alone, with a macrolide or clindamycin as alternatives for penicillin-allergic patients. 1
MRSA Coverage: Risk-Based Approach
Do not routinely add MRSA coverage for typical impetigo; reserve MRSA-active antibiotics for patients with specific risk factors. 7, 8
Indications for MRSA-Active Therapy
Add MRSA coverage only when any of the following are present:
- Penetrating trauma or injection drug use 7, 8
- Purulent drainage or exudate 7, 8
- Known MRSA colonization or prior MRSA infection 7, 8
- Failure to respond to beta-lactam therapy after 48-72 hours 7, 8
- Systemic inflammatory response syndrome (SIRS) 7, 8
MRSA-Active Oral Regimens
Clindamycin 300-450 mg orally every 6 hours for 5 days (pediatric: 10-13 mg/kg/dose every 6-8 hours) provides single-agent coverage for both streptococci and MRSA, but use only if local MRSA clindamycin resistance is <10%. 7, 8
Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily for 5 days PLUS a beta-lactam (cephalexin or amoxicillin) ensures dual coverage, as TMP-SMX lacks reliable streptococcal activity. 7, 8
Doxycycline 100 mg orally twice daily for 5 days PLUS a beta-lactam is an alternative combination, but is contraindicated in children <8 years due to tooth discoloration and bone growth effects. 7, 8
Penicillin-Allergic Patients
For non-immediate penicillin allergy, cephalexin remains acceptable because cross-reactivity is only 2-4%. 8
For immediate-type penicillin allergy, use clindamycin 300-450 mg orally every 6 hours (if local MRSA resistance <10%) or a macrolide (erythromycin) if streptococci alone are suspected. 1, 8
Critical Pitfalls to Avoid
Never use doxycycline or TMP-SMX as monotherapy for typical impetigo; they lack reliable activity against beta-hemolytic streptococci, which cause the majority of cases. 7, 8
Do not reflexively add MRSA coverage to all impetigo cases; MRSA is uncommon in typical nonpurulent impetigo even in high-prevalence settings, and routine MRSA coverage promotes resistance without improving outcomes. 7, 8
Do not extend treatment to 7-10 days based on tradition; high-quality randomized controlled trial evidence shows 5-day courses are as effective as 10-day courses for uncomplicated infections. 7
Do not continue ineffective antibiotics beyond 48-72 hours; progression despite appropriate therapy indicates either resistant organisms or a deeper infection requiring reassessment. 7
Adjunctive Measures
Cultures of vesicle fluid, pus, erosions, or ulcers establish the cause and guide targeted therapy, particularly when treatment fails or MRSA is suspected. 1
Treat predisposing conditions such as eczema, chronic skin breakdown, or nasal S. aureus colonization to reduce recurrence risk. 7
Educate patients on hygiene measures: keep draining lesions covered with clean, dry bandages and practice regular handwashing to prevent transmission. 8