Primary pathogen (Staphylococcus aureus (MSSA and CA-MRSA) — purulent SSTI; streptococci uncommonly primary in isolated abscess)
Clinical context (After adequate incision and drainage (I&D) — adjunctive oral antibiotics when clinically indicated; cephalexin for MSSA coverage without MRSA risk factors (IDSA, CHOP, CPS))
First-line therapy
Cephalexin • p.o. • 25–25 mg/kg/dose • 3×/day
Max 1000 mg/dose · Max 3000 mg/day · Duration: 5 days · 5 days from I&D when antibiotics indicated — CHOP/IDSA; step-down after IV cefazolin if hospitalized
• I&D alone may suffice: single drained abscess <2 cm without surrounding cellulitis in immunocompetent child — shared decision-making; meta-analyses show modest benefit of adjunctive antibiotics (IDSA strong, CHOP, Children's MN).
• Adjunctive cephalexin indicated: drained abscess ≥2 cm with or without cellulitis when no MRSA risk factors — faster resolution and lower recurrence vs I&D alone in many studies (CHOP, VUMC 2026, UCSF).
• Also treat with antibiotics: systemic signs (fever, SIRS), extensive surrounding cellulitis, immunocompromise, multiple lesions, facial/hand/genital involvement, age <3 months, or failed prior drainage (IDSA, CPS, NICE).
• Obtain wound culture at I&D when MRSA risk factors, recurrent abscess, treatment failure, severe infection, or immunocompromise — tailor therapy to susceptibilities (CHOP, UCSF, IDSA).
• Reassess at 48 h — progression or lack of improvement warrants culture review, MRSA-active therapy, or surgical re-evaluation (CHOP, IDSA).
Enter weight on Kids to calculate doses
Clindamycin • p.o. • 10–10 mg/kg/dose • 3×/day
Max 600 mg/dose · Max 1800 mg/day · Duration: 5 days · Covers MSSA/MRSA and streptococci if susceptible — preferred with atopic dermatitis per some pathways (Children's MN); D-test if inducible resistance concern
• Clindamycin: non-anaphylactic beta-lactam allergy, MRSA risk factors, cephalexin failure at 48 h, or atopic dermatitis (some pathways prefer clindamycin) — covers GAS and most CA-MRSA if susceptible (IDSA, CHOP, CPS).
• TMP/SMX: CPS outpatient choice for MRSA — personal/household MRSA history, high local CA-MRSA prevalence, or culture-confirmed susceptible MRSA; combine with beta-lactam if significant cellulitis and GAS not excluded (CPS, IDSA).
• TMP/SMX max dose: standard outpatient 5 mg/kg/dose TMP BID (max 160 mg TMP/dose); CHOP inpatient pathway may use 6 mg/kg/dose BID (max 320 mg TMP/dose) — not for infants <2 months (CHOP, UCSF, Children's MN).
• I&D without antibiotics: reasonable for small (<2 cm) single drained abscess without cellulitis in well-appearing immunocompetent child — discuss risks/benefits with caregivers (IDSA strong for I&D; antibiotics optional in this scenario).
• Do not use needle aspiration alone — I&D superior to ultrasound-guided aspiration for resolution at 7 days (IDSA, Children's MN).
Enter weight on Kids to calculate doses
Clinical notes
• Incision and drainage (I&D): primary treatment for all skin abscesses with fluctuance — complete drainage of loculations, packing optional per local practice; warm compresses and elevation adjunctively (IDSA strong, high).
• Drainage alone sufficient: single drained abscess <2 cm without surrounding cellulitis in immunocompetent child — antibiotics optional with shared decision-making; modest benefit of adjunctive therapy for cure/recurrence in larger abscesses (CHOP, IDSA, meta-analyses).
• Wound culture: obtain at I&D when MRSA risk factors, recurrent abscess, severe infection, immunocompromise, or failure of empiric therapy — routine culture for all drained abscesses per UCSF/CHOP to guide therapy (CHOP, UCSF, IDSA).
• Follow-up: re-examine at 48 h for clinical improvement — persistent fever, spreading erythema, or new fluctuance warrants re-drainage, culture review, MRSA-active switch, or surgical consult; total 5 days antibiotics from drainage when used (CHOP, NICE, CPS).
• IDSA — Practice guidelines for skin and soft tissue infections (purulent SSTI) (2014)
• CHOP — Cellulitis/abscess antibiotic pathway (2024)
• CPS — Community-associated bacterial SSTI in children (2024)
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• AAP Red Book — Staphylococcal and skin infections (2024)
