Infectious Disease: Impetigo

Question 1

Defintion

Answer 1

Highly contagious superficial bacterial skin infection usually caused by the gram-positive bacteira
- Staphylococcus Aureus or Steptococcus pyogenes and is typically seen in children.
- Staph Aureus causes most cases of Bullous Impetigo + 80% of Non-Bullous Impetigo

Question 2

Types of impetigo presentations

Answer 2

Non-bulbous form (MC)
Bullous form

Question 3

Types of Impetigo

Answer 3

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

Question 4

Epidemiology

Answer 4

Non-bollous impetigo = MC form
Younger children
Close contact with infected people
Other skin conditions: breakdown of epidermal barrier e.g. eczema, leads to an increased risk of bacteria invasion
Environmental factors: increased humidity and poor hygiene

Question 5

Pathophysiology

Answer 5

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 6

Signs and symptoms

Answer 6

Non-bulbous form (MC) =
- 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
Bullous form =
- Vesicles which grow to become flaccid, fluid-filled bullae
- Rupture after 2-3 days and leave a flat honey crusted lesion
- Systemic features, such as fever, diarrhoea + lymphadenopathy are more common

Question 7

Diagnosis

Answer 7

Clinical diagnosis
May be considered if there are lesions which are persistent, recurrent or widespread
Investigations to consider: swab from moist lesion or de-roofed blister for culture and sensitivity

Question 8

Management

Answer 8

General management:
- Education: washing affected areas and hands avoid scratching affected areas and avoid sharing personal skin produces
- School/work absence: children and adults should stay away from school/work until lesions are healed, dry and crusted over or 48 hours after initiation of Abx

Non-bullous impetigo
- Localised: hydrogen peroxide 1% cream or topical antibiotic e.g. fusidic acid or muprocin
- Widspread: topical (e.g. fusidic acid or mupirocin) or oral antibiotics (e.g. flucloxacillin, clarithromycin, erythromycin)

Bullous impetigo or systemically unwell or high risk of complications:
- oral Abx e.g. flucloxacillin, clarythromycin, erythromycin

Question 9

Complications

Answer 9

• Skin conditions: e.g. cellulitis and staphylococcal scalded skin syndrome
• Worsening infection: more likely to occur in neonates or bullous impetigo and can include osteomyelitis, septic arthritis , or sepsis
• Streptococcal complications: scarlet fever, urticaria, post-streptococcal glomerulonephritis , and erythema multiforme