Treatment of Cellulitis with Drainage
For cellulitis with drainage (purulent cellulitis), incision and drainage is the primary treatment, and empirical antibiotic therapy targeting CA-MRSA should be initiated pending culture results, with streptococcal coverage generally unnecessary. 1
Distinguishing Purulent vs Non-Purulent Cellulitis
The presence of drainage fundamentally changes the treatment approach:
- Purulent cellulitis (cellulitis with purulent drainage or exudate in the absence of a drainable abscess) requires empirical CA-MRSA coverage, and empirical therapy for β-hemolytic streptococci is likely unnecessary 1
- Non-purulent cellulitis (no drainage, no exudate, no abscess) is primarily streptococcal and requires β-lactam therapy targeting streptococci, with MRSA coverage only if the patient fails to respond 1
This distinction is critical because the microbiology differs substantially between these presentations 2, 3.
Source Control: Drainage Procedures
Incision and drainage is the cornerstone of treatment for any drainable collection 1:
- For simple abscesses or boils, incision and drainage alone is often adequate without antibiotics 1
- Loop drainage is preferred over traditional incision and drainage technique 3
- Ensure complete drainage before relying on antibiotic therapy, as source control is paramount 1
Antibiotic Therapy for Purulent Cellulitis
Outpatient Oral Options (5-10 days):
First-line empirical CA-MRSA coverage 1:
- Trimethoprim-sulfamethoxazole (TMP-SMX) - preferred in MRSA-prevalent areas with 91% success rate 4
- Clindamycin - effective monotherapy 1
- Doxycycline or minocycline - acceptable alternatives 1
- Linezolid - effective but expensive 1
When to Add Antibiotics to Drainage:
Antibiotic therapy is indicated when the abscess/purulent cellulitis is associated with 1:
- Severe or extensive disease involving multiple sites
- Rapid progression with associated cellulitis
- Signs of systemic illness (fever, tachycardia, hypotension)
- Comorbidities or immunosuppression
- Extremes of age
- Difficult-to-drain locations (face, hand, genitalia)
- Associated septic phlebitis
- Lack of response to drainage alone
Hospitalized Patients with Complicated Purulent SSTI:
Intravenous options for severe infections 1:
- Vancomycin IV (first-line for hospitalized patients)
- Linezolid 600 mg IV/PO twice daily
- Daptomycin 4 mg/kg IV once daily
- Telavancin 10 mg/kg IV once daily
- Clindamycin 600 mg IV/PO three times daily (if local resistance rates are low)
Treatment duration is typically 7-14 days for complicated infections 1.
Critical Pitfalls to Avoid
- Do not use β-lactams alone (cephalexin, amoxicillin) for purulent cellulitis, as they lack MRSA coverage and have significantly lower success rates (74% vs 91% for TMP-SMX) 4
- Do not prescribe antibiotics for simple abscesses that have been adequately drained without the indications listed above 1
- Do not use rifampin as single agent or adjunctive therapy for SSTI 1
- Ensure adequate drainage before assuming antibiotic failure—incomplete source control is a common reason for treatment failure 1
Risk Factors for CA-MRSA
Consider higher likelihood of MRSA in 2:
- Athletes, children, men who have sex with men
- Prisoners, military recruits
- Long-term care facility residents
- Prior MRSA exposure
- Intravenous drug users
In MRSA-prevalent areas (>60% of cultured isolates), antibiotics with CA-MRSA activity are preferred empiric therapy 4.