Antibiotic Treatment for Abscess Exudate
For simple cutaneous abscesses, incision and drainage is the primary and often sufficient treatment; however, when antibiotics are indicated, clindamycin is the preferred first-line agent because it provides coverage against both MRSA and β-hemolytic streptococci. 1, 2
When Antibiotics Are Actually Needed
Most simple abscesses achieve 85-90% cure rates with drainage alone, regardless of antibiotic use 1. Antibiotics should be added only when specific high-risk features are present: 1
- Severe or extensive disease (multiple sites of infection) or rapid progression with associated cellulitis 1
- Systemic illness signs (fever, tachycardia, hypotension) 1
- Comorbidities or immunosuppression (diabetes, HIV/AIDS, malignancy) 1
- Extremes of age (very young or elderly) 1
- Difficult drainage locations (face, hand, genitalia) 1
- Septic phlebitis 1
- Failure to respond to drainage alone 1
Outpatient Oral Antibiotic Options for MRSA Coverage
First-Line Agent
Clindamycin 300-450 mg PO three times daily is the preferred single agent because it uniquely covers both MRSA and β-hemolytic streptococci without requiring combination therapy 1, 2. This is FDA-approved for serious skin and soft tissue infections caused by susceptible staphylococci and streptococci 3.
Alternative Oral Agents (When Clindamycin Cannot Be Used)
When clindamycin is contraindicated or resistance is high, these alternatives provide MRSA coverage but require addition of a β-lactam (like amoxicillin) if streptococcal coverage is also needed: 1
- TMP-SMX 1-2 double-strength tablets twice daily - 95-100% of CA-MRSA strains are susceptible, though not FDA-approved for staphylococcal infections 1
- Doxycycline or minocycline 100 mg twice daily - effective against CA-MRSA with minocycline often more reliable when doxycycline fails 1, 4
- Linezolid 600 mg twice daily - FDA-approved but not superior to less expensive alternatives 1
Critical Dosing Considerations
- Pediatric clindamycin: 10-13 mg/kg/dose every 6-8 hours (maximum 40 mg/kg/day) 1
- Tetracyclines contraindicated in children <8 years 1
- TMP-SMX contraindicated in third trimester pregnancy and infants <2 months 1
Inpatient Parenteral Therapy for Complicated Abscesses
For hospitalized patients with complicated skin and soft tissue infections requiring IV therapy: 1
- Vancomycin 15-20 mg/kg IV every 8-12 hours - mainstay for severe MRSA infections (A-I recommendation) 1
- Linezolid 600 mg IV/PO twice daily (A-I recommendation) 1
- Daptomycin 4 mg/kg IV once daily (A-I recommendation) 1
- Clindamycin 600 mg IV/PO three times daily - if local resistance <10% and patient is stable 1
Treatment Duration
5-10 days for outpatient skin infections; 7-14 days for hospitalized complicated infections, adjusted based on clinical response 1. For MRSA specifically, a 10-day course of TMP-SMX reduces treatment failure and recurrence compared to 3 days 5.
Critical Pitfalls to Avoid
Never rely on antibiotics alone without drainage - antibiotics will fail regardless of choice if the abscess is not drained, as adequate antibiotic concentrations often do not penetrate abscess cavities 2, 6. Vancomycin and ciprofloxacin levels are particularly inadequate in most abscesses 6.
Never use rifampin as monotherapy - resistance develops rapidly and it should not be used as a single agent or even as adjunctive therapy for skin infections 1.
Avoid clindamycin for serious infections if inducible resistance (D-zone test positive) is present, though it may still work for mild infections 1, 3. Macrolide-resistant isolates should be screened for inducible clindamycin resistance 3.
Do not use TMP-SMX as monotherapy for initial cellulitis treatment without drainage, as it lacks reliable activity against β-hemolytic streptococci 1.
Culture and Susceptibility Testing
Always obtain cultures from purulent abscesses when antibiotics are prescribed, especially in severe infections, treatment failures, or suspected outbreaks 2. Culture results should guide definitive therapy, as in vitro susceptibilities do not always predict in vivo effectiveness with MRSA 4.