Cellulitis

Background

Cellulitis is an acute, spreading, pyogenic inflammation of the lower dermis and subcutaneous tissue.

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)
Mostly Strep but if pus, most are S. aureus (incl. MRSA)
Those due to penetrating trauma or in immunocompromised may be S. aureus or P aeruginosa
Bite wound infections treated differently

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 rxn	Hx exposure, pruritus, not toxic, little pain
DVT	Low (if any) fever, few skin changes
Erysipelas usually strep.	Distinct border (dermal rather than subcut. infection) Ear pinna involved (little subcut tissue so less likely cellulitis) Nasloabial fold sparing (c.f. cellulitis)
Necrotising fasciitis	Severe pain, swelling & fever; rapid progression; pain out of proportion; systemic toxicity; skin crepitus; necrosis; ecchymosis

Check blood glucose in all
WCC / CRP / d-dimers are not helpful
U&E / Creat in all
Blood cultures if SIRS (incl. >38°C), animal bite, ocular/facial infection, immersion or immunocompromised
Swab (C&S) open wounds
Imaging if suspected DVT or abscess/ostemyelitis
Surgery now if suspicion of necrotising facsiitis

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

Patients should be stratified into four classes of severity (class IV most severe) based

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).

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)
For patients post axillary clearance (lymphoedema + arm cellulitis), please refer Gen. Surg. and they will be admitted under the "Breast-on-Call" team (Ms Louise Kelly, 27/05/2024)

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.