Clinical Practice Guidelines : Cellulitis and other bacterial skin infections

Cellulitis and other bacterial skin infections

PIC Endorsed

Key points

Cellulitis is a spreading infection of the skin extending to involve the subcutaneous tissues. Many conditions present similarly to cellulitis��— always consider differential diagnoses
The typical presenting features of all skin infections include soft tissue redness, warmth and swelling, but other features are variable
Allergic reactions and contact dermatitis are frequently misdiagnosed as cellulitis. If there is itch and no tenderness, cellulitis is unlikely

Background

Cellulitis

The most common causes are Group A streptococcus (GAS) and Staphylococcus aureus. Predisposing factors include skin abrasions, lacerations, burns, eczematous skin, chickenpox, etc. although the portal of entry of organisms is often not seen

Impetigo (commonly called "school sores")��

Highly contagious infection of the epidermis, particularly common in young children.�� Causative organisms are GAS and��S. aureus
May be associated with scabies

Staphylococcal scalded skin syndrome (SSSS)��

Blistering skin disorder induced by the exfoliative (epidermolytic) toxins of S. aureus. Primarily affects neonates and young children

Necrotising fasciitis��

Rapidly progressive soft tissue infection characterised by necrosis of subcutaneous tissue
Causative organisms include GAS,��S. aureus, anaerobes and is often polymicrobial
It causes severe illness with a high mortality rate (~25%)
Recent infection with varicella is a risk factor

Cellulitis associated with water borne organisms

Aeromonas species (fresh or brackish water, and mud)
Mycobacterium marinum (fish tanks)
Vibrio species (salt or brackish water)
S. aureus, including MRSA
GAS (coral cuts)

Infected animal/human bites

Caused by different organisms and often require different treatment
Other bites are discussed elsewhere, see Snakebite, Spider bite – big black spider, Spider bite – red-back spider

There are many other forms of skin infection that are not covered in this guideline

Assessment

Typical presentation of all skin infections

Soft tissue redness
Warmth and swelling
Pain/tenderness

Mild cellulitis

Features above
No systemic features
No significant co-morbidities��

Moderate cellulitis

Features above with moderate swelling and tenderness
Systemic features (eg fever, tachycardia)

Severe cellulitis

Features above with severe swelling or tenderness
Large body surface area involved (eg larger than the patient’s handprint)
Marked systemic features (eg fever or hypothermia, tachycardia, tachypnoea, altered conscious state, unwell appearance, hypotension��— this is a late sign). See Sepsis

Features suggestive of necrotising fasciitis include:

severe pain out of keeping with apparent severity of infection
rapid progression
marked systemic features (eg high fever with rigors, tachycardia, tachypnoea, hypotension, confusion, vomiting). See Sepsis

Red flags

Abscess or suppuration
Animal or human bite
Deep structure involvement
Foreign body
Immunosuppression
Lymphangitis
MRSA infection
Multiple comorbidities
Periorbital/facial/hand involvement
Varicella associated infection

Differential diagnosis

Large local reactions to insect bites are a common mimic of cellulitis. Features include:

a punctum at the site
itch as a prominent feature
redness and induration, but rarely pain

Management

Investigations

Swab for Gram stain (charcoal / gel / bacterial transport swab and slide) and culture if discharge present
Blood culture is not useful in mild/moderate cellulitis
Consider imaging (eg ultrasound) if abscess, deep infection or foreign body suspected

Treatment

Manage sepsis if features present
Manage source if identifiable��— ie remove foreign body, drain abscess
For ongoing management refer to flowchart below

Cellulitis

Summary of antibiotic therapy

Antimicrobial recommendations may vary according to local antimicrobial susceptibility patterns; please refer to local guidelines

Cellulitis frequently looks worse after 24 hours of treatment; consider waiting 48 hours to change therapies ��
Young, unvaccinated children are at risk of

Diagnosis	Antibiotic	Total duration	Comments
Impetigo	Topical Mupirocin 2% ointment or cream to crusted areas tds��OR�� Cefalexin 20 mg/kg (max 750 mg) oral tds if widespread or large lesions	5 days	��
Mild cellulitis	Cefalexin 20 mg/kg (max 750 mg) oral tds��	5 days	��
Moderate cellulitis	A trial of oral antibiotics with close review may be considered: Cefalexin 20 mg/kg (max 750 mg) oral tds�� Consider Ambulatory/Hospital-in-the-Home (HITH) if available: Ceftriaxone 50 mg/kg (max 2g) IV daily��	5–10 days	If oral antibiotics not tolerated or no improvement after 48 hours, manage as per severe cellulitis When improving, switch to oral antibiotics as per mild cellulitis
Severe cellulitis or Staphylococcal scalded skin syndrome	Cefazolin 50 mg/kg (max 2g) IV 8H (if rapidly progressive consider adding Clindamycin 10 mg/kg (max 600 mg) IV 6H) ��	5–10 days	Consider early discharge to HITH once stable. When improving, switch to oral antibiotics as per mild cellulitis
Necrotising fasciitis	Vancomycin and Meropenem 20 mg/kg IV (max 1 g) 8H AND Clindamycin 10 mg/kg (max 600 mg) IV 6H		Urgent referral to surgical team for debridement Seek specialist advice for antibiotics Consider IVIg
Mammalian bites (uninfected / prophylactic)	Often do not need prophylactic antibiotics. When indicated: Amoxicillin/Clavulanate 80 mg/mL amoxicillin oral liquid (7:1)* 22.5 mg/kg (max 875 mg) oral bd��	5 days	��
Animal/human bites (established infection)	Amoxicillin/Clavulanate 80 mg/mL amoxicillin oral liquid (7:1) 22.5 mg/kg (max 875 mg) oral bd�� If unable to tolerate oral antibiotics: 25 mg/kg (max 1g) IV 6–8H ��	5 days (extend if severe, penetrating, involving deep tissues)	Seek specialist advice
Waterborne skin infections – seawater or fresh water	Cefalexin 20 mg/kg (max 750 mg) oral tds and Ciprofloxacin 10 mg/kg (max 500 mg) oral bd �� OR Trimethoprim/sulfamethoxazole 8/40 mg/kg (max 320/1600 mg) oral bd	5–10 days	Clean and debride wound as needed Prophylactic antibiotics are not recommended

*Indications for prophylactic antibiotics in an animal/human bite

Presentation delayed by >8 hours
Puncture wound unable to be adequately debrided
Bite on hands, feet, face
Involves deep tissues (eg bones, joints, tendons)
Involves an open fracture
Immunocompromised patient
Cat bites

Suggested antibiotic therapy where MRSA is suspected

Antimicrobial recommendations may vary according to local antimicrobial susceptibility patterns; please refer to local guidelines

Diagnosis	Antibiotic	Total duration	Comments
Mild cellulitis	Trimethoprim/sulfamethoxazole 4/20 mg/kg (max 160/800 mg) oral bd�� OR Clindamycin 10 mg/kg (max 450 mg) oral qid	5 days	��
Moderate cellulitis	A trial of oral antibiotics with close review may be considered OR Vancomycin IV	��	When improving, switch to oral antibiotics as per mild cellulitis
Severe cellulitis or Staphylococcal scalded skin syndrome	Vancomycin IV OR Clindamycin 10 mg/kg (max 600 mg) IV 6H	When improving, switch to oral antibiotics as per mild cellulitis	��

Risk factors for MRSA infection��

Residence in an area with high prevalence of MRSA, eg Northern Territory, remote communities in northern Queensland
Previous colonisation or infection with MRSA (particularly recent)
Aboriginal and Torres Strait Islander or Pacific Islander child

Consider consultation with local paediatric team when

No improvement or deterioration after 24–48 hours of therapy
Deep abscess or necrotising fasciitis suspected��— consider surgical opinion��

Consider transfer when��

Child requires care above the level of comfort of local hospital

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

Consider discharge when��

Able to tolerate oral antibiotics

Parent Information
Cellulitis
Impetigo
Staphylococcal infections
Bleach Baths

Last Updated March 2020

Reference List

Baguley D, Lim E, Bevan A, et al. Prescribing for children - taste and palatability affect adherence to antibiotics: a review. Archives of disease in childhood 2012;97(3):293-7

BMJ Online. Diagnosis and management of cellulitis. (viewed 25 November 2019)

Ibrahim LF, Hopper SM, Orsini F, Daley AJ, Babl FE, Bryant PA. Efficacy and safety of intravenous ceftriaxone at home versus intravenous flucloxacillin in hospital for children with cellulitis (CHOICE): a single-centre, open-label, randomised, controlled, non-inferiority trial. The Lancet Infectious diseases 2019;19(5):477-86

Jamal N, Teach SJ. Necrotizing fasciitis. Pediatric emergency care 2011;27(12):1195-9

Kilburn��SA, Featherstone��P, Higgins��B, Brindle��R. Interventions for cellulitis and erysipelas. Cochrane Database of Systematic Reviews 2010, Issue 6. Art. No.: CD004299. DOI: 10.1002/14651858.CD004299.pub2

Sullivan T, de Barra E. Diagnosis and management of cellulitis.��Clinical Medicine. 2018;18(2):160–163

Therapeutic Guidelines. Acute Wound Infections. (viewed 30 September 2019)

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