Cellulitis
Introduction
Erythema, edema, warmth, tender ± fever and adenopathy
Usually unilateral lower extremities
Bilateral may be due to stasis dermatitis, lymphedema, or lipodermatosclerosis
Risk:
Loss of skin integrity
Trauma
Insect/animal bite
Skin disorders (psoriasis, eczema)
Skin infection (Tinea) or ulcer
Immunocompromised (Diabetes)
Edema or vascular disease
Lymph/venous stasis
Most common pathogens beta-hemolytic streptococci (non-purulent) and S. aureus (purulent)
Erysipelas (superficial sharply demarcated) usually group A streptococcus
Investigations
Clinically assess for:
Necrotizing fasciitis – Pain out of proportion, check scrotum for Fournier gangrene
Surgical debridement and empiric antibiotics (Tazo/Clinda/Vanco IV)
Toxic shock syndrome – Pain prior to physical findings, ecchymoses, sloughing skin, hypotensive
Fluids and vasopressors for hypotension, surgical debridement, empiric antibiotics and IVIG
Gas gangrene (clostridial myonecrosis) – Fever, severe pain after surgery/trauma, crepitus
Surgery (debridement) and empiric antibiotics ± hyperbaric oxygen
Orbital cellulitis – Limitation and/or pain with eye movements, proptosis, visual changes, edema beyond eyelid, history of acute sinusitis/surgery/trauma, no improvement in 24-48 hours
Rule out extension/abscess with CT, referral to ophthalmology
Labs: WBC, CRP, creatinine, CPK, glucose (rule out diabetes in repeated infections)
Culture of pus
Culture Blood (low yield ~5%) if toxic, extensive, comorbidities, special exposures, recurrent, or persistent infection
X-ray to rule out foreign body
Ultrasound may show marbling/cobblestoning
Rule out skin abscess, gas gangrene, thrombosis
MRI to rule out osteomyelitis
Treatment
Elevation of affected area (drain edema)
Promote optimal hydration of skin without maceration
Consider compressive stockings and diuretic therapy for lymphedema and chronic venous insufficiency
Parenteral (IV) antibiotics if signs of systemic toxicity, rapid progression of erythema, immunocompromised, indwelling device or if progression of symptoms despite 48-72 hours of appropriate oral therapy
Purulent cellulitis with known MRSA (or requires coverage)
Vancomycin 15 to 20mg/kg/dose IV q8-12h (max 2g per dose)
Daptomycin 4 to 6mg/kg IV q24h
Clindamycin 900mg IV q8h
Linezolid 600mg IV q12h
Nonpurulent cellulitis or purulent with no MRSA risk factors (eg. previous MRSA, highly prevalent environment, recurrent infection) should cover for beta-hemolytic streptococci and MSSA
Cefazolin 1 to 2g IV q8h
Clindamycin 900mg IV q8h
Naficillin or Oxacillin 2g IV q4h
Pseudomonas coverage (if inadequate response, immunocompromised, prior infection)
Cefepime 2g IV q12h
Ceftazidime 1g IV q8h
Piperacillin-Tazobactam 3.375g IV q6h
Imipenem 500mg IV q6h
Meropenem 1g IV q8h
Oral Antibiotics
Purulent cellulitis with known MRSA (or requires coverage)
TMP-SMX [Septra DS] 1-2 double-strength tabs BID
Doxycycline 100mg PO BID
Minocycline 200 mg PO once, then 100 mg PO BID
Clindamycin 300 to 450 mg PO q8h
Nonpurulent with no MRSA risk factors should cover for beta-hemolytic streptococci and MSSA
Dicloxacillin 500 mg PO q6h
Amoxicillin 500 mg PO q8h
Cefadroxil 1 g PO daily (or BID)
Cephalexin 500 mg PO QID (or BID)
In children 50-100mg/kg/day PO div TID (max 3000-4500mg/day)
For penicillin allergic except those with immediate hypersensitivity consider Clarithromycin 500mg PO BID or Clindamycin
Dog/Cat/Human Bites should cover for both aerobic and anaerobic bacteria
Amoxicillin-clavulanate [Clavulin] 875/125mg PO BID
Doxycycline 100mg PO BID
For penicillin allergic and to cover for MRSA
Delayed wound closure, unless face <24h and clearly uninfected
Consider postexposure prophylaxis for rabies
Monitor animal for 10 days for rabies, if wild animal call Public health or give prophylaxis
Consider tetanus
Exposure to water should cover for AEEVM (Aeromonas species, Edwardsiella tarda, Erysipelothrix rhusiopathiae, Vibrio vulnificus, and Mycobacterium marinum)
Cephalexin 500mg PO q6h or Cefazolin 1g IV q8h or Clindamycin (if pen-allergic)
PLUS Levofloxacin 750mg PO daily
PLUS Metronidazole if soil-contaminant (covered by clindamycin)
PLUS Doxycycline if seawater exposure (to cover for Vibrio species)
Duration of therapy: 5 days if uncomplicated, extend up to 14 days if severe or slow response to therapy
References:
INESSS 2017. http://www.inesss.qc.ca/publications/clinical-guides-in-antibiotic-treatment-1st-series.html
John Hopkins Antibiotic Guide 2016. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540106/all/Cellulitis
IDSA 2014. https://academic.oup.com/cid/article-lookup/doi/10.1093/cid/ciu444
AAFP 2014. http://www.aafp.org/afp/2014/0815/p239.html