Impetigo

Question 1

What is impetigo, and what are its two main forms?

Answer 1

Impetigo is a highly contagious superficial bacterial skin infection.

•	Non-bullous impetigo (~70%): Caused by Staphylococcus aureus, Streptococcus pyogenes, or both.
•	Bullous impetigo (~30%): Caused by Staphylococcus aureus.

Question 2

How is impetigo transmitted ?

Answer 2

Impetigo is transmitted through:

• Direct contact: With infected skin via sexual or non-sexual interactions, or self-inoculation
(spreading from one part of the body to another).

• Indirect contact: Via contaminated fomites, such as shared towels, toys, or surfaces.

Question 3

What are the typical entry points for bacteria in impetigo? (3)

Answer 3

Bacteria enter through breaks in the skin, such as:

• Eczema
• Scratches
• Cuts or other minor injuries

Question 4

What is the incubation period for impetigo, and how long does it last if untreated?

Answer 4

• Incubation period: 4–10 days.

• If untreated, impetigo is self-limiting and usually resolves within 2–3 weeks, once the lesions dry out and crust over.

Question 5

What makes impetigo highly contagious ?

Answer 5

• The infection spreads easily through contact with infectious lesions.

• Crusts and discharge from these lesions harbor the bacteria, facilitating transmission.

Question 6

What are the characteristic lesions in non-bullous impetigo? (2)

Answer 6

• Thin-walled vesicles or pustules that release exudate, forming a golden/brown crust.

• Crusts dry and separate, leaving mild redness that fades.

Note: Redness may be difficult to see on darker skin tones.

Question 7

What is the progression of lesions in non-bullous impetigo? (2)

Answer 7

• Lesions crust over and dry out.

• Satellite lesions may develop due to autoinoculation (spreading infection from scratching).

Question 8

Where does non-bullous impetigo most commonly occur? (3)

Answer 8

Exposed skin areas, especially:

• Face: peri-oral (around the mouth) and perinasal (around the nose).

• Limbs

• Flexures (skin folds).

Question 9

What is one common and one uncommon symptom of non-bullous impetigo ?

Answer 9

• Lesions may be mildly itchy or painful.

• Systemic symptoms (e.g., fever) are uncommon.

Question 10

How does autoinoculation contribute to non-bullous impetigo?

Answer 10

Scratching or touching infected areas can spread bacteria to nearby skin, leading to the development of satellite lesions.

Question 11

What type of lesions are characteristic of bullous impetigo?

Answer 11

• Flaccid, fluid-filled vesicles or blisters (1–2 cm in diameter), Surrounding skin shows no redness.

Question 12

How long do the vesicles or blisters of bullous impetigo persist?

Answer 12

• They persist for 2–3 days.

Question 13

In which population is bullous impetigo likely to be widespread, and what systemic symptoms may occur?

Answer 13

• Can be widespread in infants.

• If widespread, systemic symptoms such as fever may occur.

Question 14

Is impetigo self-limiting, and why might treatment still be considered?

Answer 14

• Yes, impetigo is self-limiting, typically resolving within 2–3 weeks.

• Treatment may be considered to speed up recovery and reduce the risk of spreading.

Question 15

What is the first-line treatment for localised impetigo and how often is it applied?

Answer 15

• Hydrogen peroxide 1% cream, applied bd (twice daily) or tds (three times daily) for 5 days.

Question 16

What alternatives are available if hydrogen peroxide cream is unsuitable for localised impetigo?

Name two examples (2)

Answer 16

• Topical antibiotics applied tds (three times daily) for 5 days, with the option to extend to 7 days if required:
Examples:

• Fusidic acid 2%.
• Mupirocin 2%, if fusidic acid resistance is present.

Question 17

How is widespread impetigo treated, and what factors influence the choice of treatment? (4)

Answer 17

Treatment involves a short course of topical or oral antibiotics.

Factors influencing treatment choice include:
• Patient preference.
• Practicalities of administration.
• Adverse drug reaction (ADR) risk.
• Antibiotic resistance risk.

Question 18

What are the treatment options for widespread impetigo?

Answer 18

• Topical treatment:
Same as for localised impetigo.

Oral antibiotics
• Flucloxacillin qds (four times daily) for 5 days (can increase to 7 days if required).

Question 19

When should impetigo cases be referred to a GP? (4)

Answer 19

• If bullous impetigo is present.
• If the condition is recurrent.
• If the patient is at high risk of complications.
• If systemic symptoms are observed.

Question 20

What is the first-line oral antibiotic prescribed for impetigo?

Answer 20

• Flucloxacillin:
Dosage: qds (four times daily) for 5 days.
May increase to 7 days if necessary.

Question 21

What are the alternative treatments for impetigo if the patient is penicillin-allergic? (2)

Answer 21

• Clarithromycin bd (twice daily) for 5 days.

• Erythromycin is used during pregnancy as a safe alternative.

Question 22

What are some practical measures that can be taken for patients with impetigo ? (8)

Answer 22

•Wash affected areas with soap and water, pat dry

•Wash their hands regularly, in particular after touching a patch of impetigo

•Avoids scratching affected areas

•Cover patches with loose clothing or gauze bandages

•Avoids sharing towels, face cloths, and other personal care products and thoroughly cleans potentially contaminated toys and play equipment

•Wash sheets, towels etc at high temperature

•Wash/wipe down toys with detergent and warm water

•Children and adults should stay away from nursery/school/work until all lesions are healed, dry and crusted over, or until 48 hours after initiation of treatment (antibiotics and/or hydrogen peroxide cream) – avoid contact sport, gym