Impetigo Flashcards
What is impetigo?
Impetigo is a common, superficial bacterial skin infection
What are the two main types of impetigo?
Non-bullous — accounts for about 70% of cases.
Bullous — skin eruption is characterized by bullae (fluid-filled lesions over 1 cm in diameter).
How can impetigo be further classified?
Primary — direct bacterial invasion of otherwise healthy, intact skin.
Secondary — bacterial infection through a break in the skin, for example, from trauma (such as a cut, burn, or insect bite) or an underlying skin condition (such as eczema or scabies).
How is impetigo commonly spread?
It is most commonly spread through direct contact with an infected person, including contact with drainage from impetigo lesions.
Autoinoculation via fingers or contaminated objects (such as toys, towels, or clothing) often leads to satellite lesions in adjacent areas.
What is the incubation period for impetigo?
The incubation period, from skin colonization to the development of the characteristic lesions, is 4–10 days.
What pathogen is non-bullous impetigo caused by?
Non-bullous impetigo is caused by S. aureus (80% of cases), S. pyogenes (10% of cases), or both (10% of cases). Disruption in skin integrity allows for bacterial invasion via the interrupted surface.
What is bullous impetigo caused by?
Bullous impetigo is almost always caused by S. aureus
What is the pathophysiology for bullous impetigo?
Bullae (fluid-filled lesions) form when exfoliative toxins produced by S. aureus cause loss of cell adhesion in the superficial epidermis by targeting intracellular adhesion molecules (desmoglein – 1) in the epidermal granular layer. Bullous impetigo can affect intact skin.
What other pathogen can cause non-bullous impetigo?
Meticillin-resistant Staphylococcus aureus (MRSA) can be a causative organism and is seen more often in cases of non-bullous impetigo.
Name 6 risk factors for impetigo
- Conditions that lead to breaks in the skin, such as cuts, burns, insect bites, eczema, or contact dermatitis.
- Warm/humid weather.
- Poor hygiene.
- Crowded and impoverished environments.
- Comorbidities that predispose to immunosuppression, such as diabetes and malnutrition.
- Contact with a person with impetigo.
What age is non-bullous impetigo most common?
Non-bullous impetigo (approximately 70% of cases) is most common in children aged 2–5 years
What age is bullous impetigo most common?
Bullous impetigo is reported most often in children aged under 2 years
Without treatment how long does the impetigo take to heal?
7-21 days
Name 6 complications associated with impetigo
1) cellulitis
2) sepsis
3) scarring
4) post-Streptococcal glomerulonephritis
5) Staphylococcus scalded skin syndrome
6) Scarlet-fever
What should be included in an impetigo history?
The presenting symptoms including onset, duration, and location of lesions.
Recent trauma to the skin, for example, a bite, burn, or laceration.
Underlying comorbidities that predispose to infection, such as a skin condition (such as eczema) or diabetes mellitus.
Other risk factors for impetigo, for example, recent contact with a person with impetigo.
Previous treatment, including antimicrobial treatment.
Systemic features, such as fever.
What is the characteristic feature of impetigo infection?
golden crust
How is non-bullous impetigo characterised?
by thin-walled vesicles or pustules that rupture quickly, forming golden-brown crusts.
How do non-bullous impetigo begin?
It starts as maculopapular lesions, which evolve into vesicles or pustules that rupture easily and are seldom seen on clinical examination.
The exudate dries to form golden-brown crusts, which are thicker in streptococcal infections.
Which anatomical landmarks are the most common site for impetigo?
- Face (especially around the nose and the mouth)
- limbs
- flextures (especially around the axillae)
When may satellite lesions develop?
Following autoinoculation
True or false: non-bullous impetigo commonly presents with systemic symptoms e.g. fever
false
True or false: bullous impetigo commonly presents with systemic symptoms
True
Describe the clinical presentation associated with bullous impetigo:
1-2cm itchy, painful fluid filled vesicles on the skin which grow and burst, forming a golden crust
How do lesions typically present?
Lesions are usually asymptomatic, with occasional pruritus. There is minimal or no surrounding erythema.
What investigations are used when concerning impetigo?
Consider swabs (of exudate from a moist lesion or de-roofed blister) for culture and sensitivities if:
-The person fails to respond to appropriate empirical treatment.
-Impetigo is recurrent or widespread.
-There is doubt about the diagnosis.
-Meticillin-resistant Staphylococcus aureus (MRSA) is suspected (for example, if a spontaneous abscess or cellulitis develops or impetigo is persistent or recurrent).
What are some bacterial differential diagnosis’ for impetigo?
- Erysipelas — sharply demarcated erythematous plaques, typically unilateral and on the face. Oedema and warmth are common features.
- Staphylococcal scaled skin syndrome — an uncommon, superficial, blistering skin condition characterized by widespread erythema and exfoliation
- Necrotising fasciitis - a destructive and rapidly progressive soft tissue infection involving deep subcutaneous tissue
- Cellulitis
What are some fungal differential diagnoses’ for impetigo?
- tinea corporis
- Candidiasis
- Tinea capitis
What are some viral differential diagnoses for impetigo?
- Chicken pox
- Herpes simplex
What are some non-infective differential diagnoses for impetigo?
- Drug reaction
- Atopic/contact dermatitis
- Eczema
- Insect bites
- Burns/Scalds
When should a patient with non-bullous impetigo be referred to the hospital?
- A serious complication is suspected
- The patient is immunosuppressed
- They are systemically unwell
- Impetigo reoccurs frequently
- The diagnosis isn’t certain
What hygiene measures should a patient with non-bullous impetigo take?
- Wash affected areas with soap and water
- Avoid touching/scratching impetigo
- Cover the affected areas where possible
- Do not share towels/ facecloths/ personal products
- Clean equipment
- Wash clothing and bedding at hottest available setting
What treatment is given to a patient with non-bullous impetigo who is not systemically unwell?
Consider offering hydrogen peroxide 1% cream (to be applied two to three times daily for 5 days).
If hydrogen peroxide 1% cream is unsuitable, offer topical fusidic acid 2% (to be applied three times daily for 5 days).
If fusidic acid resistance is suspected or confirmed, offer topical mupirocin 2% (to be applied three times daily for 5 days).
What treatment is given to a patient with non-bullous impetigo who is systemically unwell?
Offer one of the following:
Topical fusidic acid 2% (to be applied three times daily for 5 days) — if fusidic acid resistance is suspected or confirmed, offer topical mupirocin 2% (to be applied three times daily for 5 days).
An oral antibiotic. (Flucloxacillin)
What is the treatment of bullous impetigo?
oral/IV flucloxacillin
What is widespread bullous impetigo called?
Staphylococcus scaled syndrome
