Impetigo

Question 1

Definition

Answer 1

Superficial bacterial skin infection typically seen in children usually caused by:
- Gram-positive bacteria Staphylococcus aureus
- Streptococcus pyogenes

Question 2

Epidemiology

Answer 2

Non-bullous impetigo is the most common form (70% of cases).
- Age: younger children
- Close contact with infected people
- Other skin conditions: breakdown of the epidermal barrier, e.g. eczema , leads to an increased risk of bacterial invasion
- Environmental factors: increased humidity and poor hygiene

Question 3

Types of impetigo

Answer 3

• non-bullous form (most commonly)
• bullous form= Staphylococcus aureus causes almost all cases of bullous impetigo and accounts for the majority of cases (80%) of non-bullous impetigo.

Question 4

Pathophysiology

Answer 4

• The bacteria invade the superficial layers of the epidermis leading to macule formation . Once a lesion is present, self-inoculation to other sites is common .
• In non-bullous impetigo, the lesion will develop into a vesicle or pustule and coalesce before rupturing. Once ruptured, the exudate forms a characteristic honey-coloured crust with an erythematous base .
• In bullous impetigo, vesicles appear and become flaccid bullae before rupturing.

Question 5

Primary vs secondary impetigo

Answer 5

• Primary impetigo occurs in previously normal skin by direct bacterial invasion.
• Secondary impetigo involves infecting a wound site or skin affected by another condition.

Question 6

Bullous signs and symptoms

Answer 6

• Vesicles which grow to become flaccid, fluid-filled bullae.
• Rupture after 2-3 days and leave a flat honey crusted lesion.
• Common systemic features e.g.
  = fever
  = diarrhoea
  = lymphadenopathy

Question 7

Non-bullous signs and symptoms

Answer 7

• Honey crusted lesions after vesicles have ruptured (rupture very early in disease course)
• Lesions can anywhere on the body (most likely face/chin)
• Systemic features are less common

Question 8

Diagnosis

Answer 8

Clinical diagnosis
Investigations considered if there are lesions which are persistant:
- Swab: exudate from a moist lesion or de-roofed blister for culture and sensitivity

Question 9

Treatment general

Answer 9

Education:
- washing affected areas and hands,
- avoid scratching affecting areas and
- avoid sharing personal care products
School/work absence: everyone should stay away from school/work until lesions are healed, dry and crusted over or 48 hours after the initiation of antibiotics

Question 10

Non-bullous impetigo

Answer 10

• Localised: ​​Hydrogen peroxide 1% cream or topical antibiotic, e.g. fusidic acid or mupirocin
• Widespread: topical (e.g. fusidic acid or mupirocin) or oral antibiotics (e.g. flucloxacillin, clarithromycin, erythromycin)

Question 11

Bullous impetigo treatment or systemically unwell or high risk of complications

Answer 11

Oral antibiotics: e.g.
- flucloxacillin,
- clarithromycin,
- erythromycin