Uncomplicated Cellulitis

Exclusion Criteria

Skin and skin structure infections (SSSI) in immunocompromised hosts, surgical wounds. Refer to MRSA Skin and Soft Tissue Infection if there is a high clinical suspicion of MRSA infection.

Laboratory Diagnosis

  • Obtain blood cultures only in the presence of systemic toxicity (fever / hypothermia, tachycardia, or hypotension)
  • Culture of fluid or pus in a sterile container is preferred to a swab. Indicate anatomic site of infection and any significant epidemiology.

Uncomplicated cellulitis (i.e. mild and localized, not involving the head)

  • *Excludes diabetic foot ulcer, animal or human bites*
  • Common pathogens: Staphylococcus aureus, beta-hemolytic streptococcus such as Streptococcus pyogenes (group A streptococcus)
  • Can usually be managed with PO antibiotics
  • 5 days of treatment is often sufficient in settings of uncomplicated cellulitis

Empiric Therapy

Cephalexin 500mg po QID (doses up to 1g/DOSE may be used in obese patients)

In cases of severe beta lactam allergies (e.g. angioedema, bronchospasm, anaphylaxis etc): Clindamycin 300-450mg po QID

Uncomplicated cellulitis where intravenous is required initially for first 48-72 hours (e.g. unable to tolerate po, extensive infection):
Cefazolin 1-2 g IV q8h OR Cloxacillin 1-2 g IV q6h

In cases of severe beta lactam allergies:
Vancomycin 15mg/kg IV q12h (renal adjustment is required) OR Clindamycin 600mg IV q8h

MRSA Skin & Soft Tissue Infection

Consider empiric MRSA coverage, in particular in patients with: Purulent skin infections that do not resolve with penicillin/cephalosporin therapy, known colonizers of MRSA, and in patients with increased risk for MRSA based on local epidemiology, e.g. IV drug users.

Oral Therapy (Uncomplicated MRSA Infection)

  • Consider incision and drainage
  • Usual treatment duration is 5-10 days but should be based on patient’s clinical response

Preferred

  • Trimethoprim/sulfamethoxazole (TMP/SMX) 10-15mg/kg/DAY (trimethoprim) in 2-4 divided doses
    • TMP/SMX lacks activity against group A Streptococci. Consider use in combination with cephalexin for empiric treatment of cellulitis

Alternatives

  • Doxycyline 100mg po BID OR
  • Clindamycin 300-450mg po QID

Parenteral Therapy (Complicated MRSA Infection)

Vancomycin 15mg/kg IV q12h (renal dosage adjustment is necessary)

  • Alternatives include linezolid (po/IV) and daptomycin (IV). Please note that these require Infectious Diseases endorsement