Impetigo

Question 1

What is impetigo?

Answer 1

Impetigo is a common, superficial bacterial skin infection

Question 2

What are the two main types of impetigo?

Answer 2

Non-bullous — accounts for about 70% of cases.
Bullous — skin eruption is characterized by bullae (fluid-filled lesions over 1 cm in diameter).

Question 3

How can impetigo be further classified?

Answer 3

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).

Question 4

How is impetigo commonly spread?

Answer 4

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.

Question 5

What is the incubation period for impetigo?

Answer 5

The incubation period, from skin colonization to the development of the characteristic lesions, is 4–10 days.

Question 6

What pathogen is non-bullous impetigo caused by?

Answer 6

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.

Question 7

What is bullous impetigo caused by?

Answer 7

Bullous impetigo is almost always caused by S. aureus

Question 8

What is the pathophysiology for bullous impetigo?

Answer 8

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.

Question 9

What other pathogen can cause non-bullous impetigo?

Answer 9

Meticillin-resistant Staphylococcus aureus (MRSA) can be a causative organism and is seen more often in cases of non-bullous impetigo.

Question 10

Name 6 risk factors for impetigo

Answer 10

1. Conditions that lead to breaks in the skin, such as cuts, burns, insect bites, eczema, or contact dermatitis.
2. Warm/humid weather.
3. Poor hygiene.
4. Crowded and impoverished environments.
5. Comorbidities that predispose to immunosuppression, such as diabetes and malnutrition.
6. Contact with a person with impetigo.

Question 11

What age is non-bullous impetigo most common?

Answer 11

Non-bullous impetigo (approximately 70% of cases) is most common in children aged 2–5 years

Question 12

What age is bullous impetigo most common?

Answer 12

Bullous impetigo is reported most often in children aged under 2 years

Question 13

Without treatment how long does the impetigo take to heal?

Answer 13

7-21 days

Question 14

Name 6 complications associated with impetigo

Answer 14

1) cellulitis
2) sepsis
3) scarring
4) post-Streptococcal glomerulonephritis
5) Staphylococcus scalded skin syndrome
6) Scarlet-fever

Question 15

What should be included in an impetigo history?

Answer 15

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.

Question 16

What is the characteristic feature of impetigo infection?

Answer 16

golden crust

Question 17

How is non-bullous impetigo characterised?

Answer 17

by thin-walled vesicles or pustules that rupture quickly, forming golden-brown crusts.

Question 18

How do non-bullous impetigo begin?

Answer 18

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.

Question 19

Which anatomical landmarks are the most common site for impetigo?

Answer 19

1. Face (especially around the nose and the mouth)
2. limbs
3. flextures (especially around the axillae)

Question 20

When may satellite lesions develop?

Answer 20

Following autoinoculation

Question 21

True or false: non-bullous impetigo commonly presents with systemic symptoms e.g. fever

Answer 21

false

Question 22

True or false: bullous impetigo commonly presents with systemic symptoms

Answer 22

True

Question 23

Describe the clinical presentation associated with bullous impetigo:

Answer 23

1-2cm itchy, painful fluid filled vesicles on the skin which grow and burst, forming a golden crust

Question 24

How do lesions typically present?

Answer 24

Lesions are usually asymptomatic, with occasional pruritus. There is minimal or no surrounding erythema.

Question 25

What investigations are used when concerning impetigo?

Answer 25

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).

Question 26

What are some bacterial differential diagnosis’ for impetigo?

Answer 26

1. Erysipelas — sharply demarcated erythematous plaques, typically unilateral and on the face. Oedema and warmth are common features.
2. Staphylococcal scaled skin syndrome — an uncommon, superficial, blistering skin condition characterized by widespread erythema and exfoliation
3. Necrotising fasciitis - a destructive and rapidly progressive soft tissue infection involving deep subcutaneous tissue
4. Cellulitis

Question 27

What are some fungal differential diagnoses’ for impetigo?

Answer 27

1. tinea corporis
2. Candidiasis
3. Tinea capitis

Question 28

What are some viral differential diagnoses for impetigo?

Answer 28

1. Chicken pox
2. Herpes simplex

Question 29

What are some non-infective differential diagnoses for impetigo?

Answer 29

1. Drug reaction
2. Atopic/contact dermatitis
3. Eczema
4. Insect bites
5. Burns/Scalds

Question 30

When should a patient with non-bullous impetigo be referred to the hospital?

Answer 30

1. A serious complication is suspected
2. The patient is immunosuppressed
3. They are systemically unwell
4. Impetigo reoccurs frequently
5. The diagnosis isn’t certain

Question 31

What hygiene measures should a patient with non-bullous impetigo take?

Answer 31

1. Wash affected areas with soap and water
2. Avoid touching/scratching impetigo
3. Cover the affected areas where possible
4. Do not share towels/ facecloths/ personal products
5. Clean equipment
6. Wash clothing and bedding at hottest available setting

Question 32

What treatment is given to a patient with non-bullous impetigo who is not systemically unwell?

Answer 32

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).

Question 33

What treatment is given to a patient with non-bullous impetigo who is systemically unwell?

Answer 33

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)

Question 34

What is the treatment of bullous impetigo?

Answer 34

oral/IV flucloxacillin

Question 35

What is widespread bullous impetigo called?

Answer 35

Staphylococcus scaled syndrome