Background
Cellulitis is an acute, spreading, pyogenic inflammation of the lower dermis and subcutaneous tissue.
- Incidence rising
- Majority - S. pyogenes or Staph aureus
- MRSA and VLE versions emerging
- Dx is clinical
- Classified using Dundee criteria
Risk factors
- Venous insufficiency
- Lymphoedema (also a complication)
- Peripheral vascular disease
- Diabetes mellitus
- Obesity
- Tinea pedis
- Local ulcers, trauma, insect bites
Diagnosis
- Clinical
- Usually lower limb
- Acute, tender, erythematous, swollen area
- ± ill-distinct margin (subcut. rather than skin infection)
- ± blisters
- ± ulcers
- ± oedema
- Classically ascending lymphangitis
- Regional adenitis
- Fever, Malaise
- Beware sepsis (See SIRS)
Differential Dx
Treatment recommendations for cellulitis based on organisms
| Stasis dermatitis | Absence of pain or fever; circumferential; bilateral |
|---|---|
| Acute arthritis | Involvement of joint; pain on movement |
| Pyoderma gangrenosum | IBD Hx, Local ulceration |
| Hypersensitivity/drug reaction | Hx exposure, pruritus, not toxic, little pain |
| DVT | Low (if any) fever, few skin changes |
| Necrotising fasciitis | Severe pain, swelling and fever; rapid progression; pain out of proportion; systemic toxicity; skin crepitus; necrosis; ecchymosis |
Investigations
- Check blood glucose (or BM) in all
- WCC / CRP / d-dimers are not helpful
- U&E / Creat in all
- Blood cultures only if significant systemic upset including pyrexia (>38°C).
- Swab (C&S) open wounds.
- Imaging if suspected DVT or abscess/ostemyelitis.
- MRI if suspicion of necrotising facsiitis.
Treatment
- Analgesia
- Treat the patient, not the test
- Rest, elevation, analgesia ± VTE thromboprophylaxis
- Mark the area
- IV or PO antibiotics
- Beware SIRS
- Beware possibility MRSA or VLE in susceptible patients
- Admit CDU if IV antibiotics required and no SIRS
- Out patient IV antibiotics only after discharge from CDU
Atypical Scenarios
| Clinical | Organism | Antibiotic (nchd.ie) |
|---|---|---|
| Typical cellulitis | Strep. pyogenes | Clindamycin or Amoxicillin or Flucloxacillin |
| Typical cellulitis—pus forming | Staph. aureus | Clindamycin or Flucloxacillin |
| Penicillin allergy | NA | Clindamycin or Clarithromycin |
| Cat or dog bite | Pasteurella multocida | Co-amoxiclav; if allergic to penicillin: doxycycline and metronidazole |
| Freshwater exposure | Aeromonas hydrophila | Ciprofloxacillin |
| Salt-water exposure | Vibrio vulnificus | Doxycycline |
| Necrotising fasciitis | Clostridium perfringens | Benzylpenicillin, ciprofloxacillin, and clindamycin |
| Butchers and fish handlers | Erysipelothrix | Ciprofloxacillin |
Dundee classification of severity
Patients should be stratified into four classes of severity (class IV most severe) based
- Sepsis
- Co-morbidity
- Standardized early warning score (SEWS).
SIRS = ≥2 of: <4 WCC >12, <36° Temp >.388C, HR > 90, RR >20
Further details to follow - but class 3 (significant co-morbidities or SIRS features are not suitable for CDU).
CDU (CUH) patients
For CDU patients please start either:
- Cefazolin 2g q24h iv plus probenicid 1g po q24h if CIT suitable or
- Flucloxacilin (± penicillin) (more on nchd.ie).
Cefazolin / Probenicid
More details on home IV antibiotics for cellulitis.
If the patient is unable to tolerate the once daily regimen due to GI upset, then prescribe Cefazolin 2g twice daily iv without the probenacid.
Check dosing (with pharmacist) in renal impairment.
For penicillin allergic (OPAT/CIT only) patients, please contact micro. for advice on vancomycin dosing and monitoring.
Probenecid contra-indicated with:
- Methotrexate
- Sodium phenylbutyrate
- Ketorolac
- Pyrazinamide
- High dose aspirin
- Dapsone
- Heparin
- Fosfomycin
Links
https://www.nchd.ie (hospital specific we app for clinicians)
UK Support group forum for cellulitis patients
Marwick C et al . Severity assessment of skin and soft tissue infections ..... J Antimicrob Chemother