RECOGNITION AND ASSESSMENT

  • Acute spreading bacterial infection below skin surface

Symptoms and signs

  • Unilateral limb redness
    • in patients with bilateral red legs a diagnosis of bilateral cellulitis is extremely unlikely, consider other diagnoses – refer to Integrated red leg service or dermatology
  • Erythema
  • Warmth
  • Swelling – may be fluctuant
  • Tenderness/pain
  • Demarcation
  • Crepitus
  • Pyrexia

Non-severe

  • Systemically well with temperature 36–38°C
  • Cellulitis not involving face or hand
  • Not previously treated with adequate oral antimicrobials for the same complaint

Severe

  • If any of the following present:
    • lesion spreading rapidly
    • systemic features (e.g. temperature >38°C or <36°C, hypotension, tachycardia)
    • cellulitis involving face or hand
    • progression despite adequate doses of appropriate oral antimicrobials
    • significant co-morbidities (e.g. asplenia, neutropenia, cirrhosis, immunocompromised, cardiac or renal failure, or pre-existing oedema)
    • blistering/bullae, superficial haemorrhage into blisters, dermal necrosis. Lymphangitis and lymphadenopathy may occur

Likely organisms

  • Staphylococcus aureus
  • Streptococcus group A
  • Anaerobes, particularly in patients with diabetes and/or ischaemic limbs

Those at risk

  • Lymphoedema/chronic oedema
  • Diabetes mellitus
  • Intravenous drug user
  • Immunocompromised
  • Peripheral vascular disease

Investigations

  • FBC
  • U&E
  • CRP
  • ESR
  • If systemically unwell and/or history of MRSA in previous 2 yr:
    • blood culture specimen – see Collection of blood culture specimens guideline
  • Swab from:
    • portal of entry or aspirate of pus
    • cannula site and tip for culture (if source)
    • if skin broken – swab for microbiology
    • screen for MRSA if not screened in prior 7 days
  • If osteomyelitis suspected, plain X-ray
    • if X-ray normal, this does not rule out osteomyelitis; consider MRI scan
  • Outline periphery of erythema with pen (indelible ink if possible)
  • If bloods are normal, cellulitis is unlikely

Differential diagnosis

  • If upper or lower limb involved, consider DVT in the presence of any of the following:
    • entire limb swollen for <3 months
    • previously documented DVT
    • active cancer (treatment within 6 months, ongoing or palliative)
    • paralysis, paresis or recent immobilisation
    • local tenderness along distribution of deep venous system
    • calf circumference >3 cm larger than asymptomatic leg (measured 10 cm below tibial tuberosity)
  • If bilateral with no systemic malaise, consider:
    • varicose eczema (bilateral with crusting, scaling, itch or other eczema)
    • contact dermatitis (as above but with clear demarcation often below knee where bandaging may have been in situ)
    • acute liposclerosis (pain, redness and swelling but patient systemically well)
  • Lymphangitis
  • Abscess
  • Ulcers
  • Necrotising fasciitis
  • Osteomyelitis
  • Thrombophlebitis

IMMEDIATE MANAGEMENT

  • Baseline observations:
    • temperature
    • pulse
    • blood pressure
    • blood glucose
  • If systemic sepsis, see Sepsis management guideline
  • If orbital cellulitis, seek urgent ophthalmology opinion and discuss choice of antimicrobials with consultant microbiologist/in infectious diseases
  • If patient unwell with pain out of proportion to local findings or shows evidence of marked systemic toxicity, consider necrotising fasciitis. Request senior review and consider urgent surgical opinion
  • Fluid resuscitate if necessary, see Adult fluid management guideline
  • Treat underlying cause (e.g. portal of entry such as tinea pedis)
  • Remove source of infection (e.g. cannula)

Penicillin Allergy

  • True penicillin allergy is rare
  • Ask the patient and record what happened when they were given penicillin
  • If any doubt about whether patient is truly allergic to penicillin, seek advice from a microbiologist or consultant in infectious diseases
Accept penicillin allergy as genuine hypersensitivity only if history of either rash within 72 hr of dose or anaphylactic reaction is convincing

Infection Control alerts

  • Check for IC alert
    • If IC alert not available, check previous 12 months of microbiology reports
  • If MRSA present, treat as tagged for MRSA. See MRSA management
  • If ESBL, MGNB, CARB present, treat as tagged for ESBL. See ESBL/MGNB/CARB management

Choice of antimicrobials:

  • Seek urgent ophthalmology opinion and discuss choice of antimicrobials with consultant microbiologist/in infectious diseases
  • Vancomycin IV by infusion – see Vancomycin calculator & guideline
  • If improving after 48 hr, discuss suitable alternative oral agents with microbiologist or consultant in infectious diseases
  • First line: Flucloxacillin 2 g IV 6-hrly.
    • oral stepdown: Flucloxacillin 1 g oral 6-hrly once apyrexial and skin lesions improving (e.g. 50% reduction in extent of initial erythema) unless blood culture has become positive
  • Alternative (true penicillin allergy): Vancomycin IV by infusion aiming for vancomycin concentration of 15–20 mg/L – see Vancomycin calculator & guideline.
    • oral stepdown: Doxycycline 200 mg oral first day then doxycycline 100 mg oral daily once apyrexial and skin lesions improving (e.g. 50% reduction in extent of initial erythema) unless blood culture has become positive or organism resistant to doxycycline has been reported
  • First line: Flucloxacillin 1 g oral 6-hrly
  • Alternative (true penicillin allergy): Doxycycline 200 mg oral first day then doxycycline 100 mg oral daily

SUBSEQUENT MANAGEMENT

  • Outline and monitor size of affected area daily

Duration of treatment

  • If no response after 24-48 hr of antimicrobial treatment or patient becoming more septic or necrotising fasciitis suspected, discuss with consultant microbiologist/in infectious disease
  • Severe: 7–14 days total (including IV treatment) unless blood culture has become positive
  • Non-severe: 5–7 days total

DISCHARGE AND FOLLOW-UP

  • If patient does not require admission or is fit for discharge but needs IV antimicrobials, refer to outpatient (OPAT) service for IV antimicrobials at home
  • If redness is bilateral (or unilateral and DVT has been excluded) with no systemic malaise, refer to Integrated Red Legs Service (IRLS)

© 2022 The Bedside Clinical Guidelines Partnership.

Created by University Hospital North Midlands and Keele University School of Computing and Mathematics.

Research and development team: James Mitchell, Ed de Quincey, Charles Pantin, Naveed Mustfa