Home CPD Impetigo: a brief overview

Impetigo: a brief overview

December 9, 2022

Case Scenario

Patrick, 4 years old, has a rash around his nose and mouth. You recognise the honeycoloured crust as a typical presentation for impetigo. Patrick has no other symptoms, other medicines or medical conditions. Impetigo requires antibiotic treatment, so you refer his mother to their medical practitioner for confirmation and a prescription for treatment.

Learning objectives

After reading this article, pharmacists should be able to:

Describe the signs and symptoms of impetigo
Discuss the risk factors for developing impetigo
Explain the management approach for impetigo
Discuss the medicines used for treatment of impetigo

Competency (2016) standards addressed: 1.1, 1.4, 1.5, 3.1, 3.2, 3.5

Accreditation number: CAP2212OTCBG

Accreditation expiry: 30/11/2025

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Introduction

Impetigo is a highly contagious bacterial skin infection common in children. It is usually mild and self-limiting but can be uncomfortable, unsightly and can rarely lead to serious sequelae.^1-5

What are the signs and symptoms?

Non-bullous impetigo is the most common form. It typically occurs on the face, especially the perioral region, or the extremities where skin may be damaged.^1,^3,⁵

It starts with a single erythematous macule that changes into a pustule or vesicle, which then ruptures, forming a characteristic yellowish-brown (honey-coloured) crust.^1,⁴ The lesion is often itchy.

Systemic symptoms don’t usually occur, and scarring is uncommon.^1-4 Bullous impetigo occurs on the face, trunk, extremities, buttocks, axilla and perineal regions.^1,⁵ It appears as thin-roofed bullae filled with yellow fluid which break, leaving a scaly rim.^1,^3,⁵ It can be associated with systemic symptoms such as malaise, fever and lymphadenopathy.^1,⁵.

What are the causes and risk factors?

Impetigo affects about 162 million children worldwide at any time.6 It can be endemic in remote communities and is a common complication of scabies.^2,⁷ Non-bullous impetigo is caused by Staphylococcus aureus or Streptococcus pyogenes, or sometimes both, infecting the epidermis. A deeper form, ecthyma, ulcerates and infects the dermis, leaving a scar.¹ S. aureus is more common in non-endemic settings, and S. pyogenes is more common in endemic settings.² Bullous impetigo is caused by S. aureus infecting the epidermis and producing exfoliative toxins that cause the epidermal granular layer to separate and form bullae.¹

Impetigo is very contagious. It can spread by autoinoculation (e.g. by scratching) and can be transmitted to others by direct or indirect contact with lesions (e.g. via clothing or towels).^1,^3,⁵ It can occur at any age but is more common in young children (hence the common name “school sores”) and in people who are immunosuppressed.

A warm humid climate, poor hygiene and crowded environments also increase its risk.^1,^5,⁶ Infection is more common in areas of dry skin, where skin integrity is disrupted by another disease (e.g. eczema, scabies, chickenpox) or where there is skin trauma. Bullous impetigo can occur on healthy skin.^1,^5,⁶ A proportion of the healthy population are carriers of S. aureus, especially in the nostrils and flexures.

This can be the cause of recurrent impetigo.^1-3,⁸ Impetigo is typically mild and self-limiting; however, rarely there may be serious sequelae, especially if it is left untreated. These include^1,^4,⁶:

cellulitis, lymphangitis, bacteraemia and septicaemia
staphylococcal scalded skin syndrome
scarlet fever
post-streptococcal glomerulonephritis
streptococcal toxic shock syndrome

There is also a possible association between S. pyogenes impetigo and acute rheumatic fever and rheumatic heart disease, however the link is uncertain.^5-7,⁹

How is it diagnosed?

Impetigo is diagnosed clinically by its characteristic appearance. Lesions commonly occur in areas readily observable in a community pharmacy.^1,⁵ Skin swabs may be required if impetigo is recurrent, widespread or if there is suspicion of methicillin-resistant S. aureus (MRSA).^1,¹⁰ Nasal swabs for identifying staphylococcal carriage may be required if impetigo is recurrent.^1,¹⁰

Differential diagnoses of impetigo include many other blistering and rash disorders, however its distinctive appearance aids diagnosis.^1,^3,⁵

When is referral required?

Impetigo requires antibiotic treatment; all patients will need referral to a doctor for a prescription.^1,^2,¹⁰, If there is worsening of symptoms, no response to treatment, or reinfection, pharmacists should refer the patient to a medical practitioner for further review.^1,³

What is the management approach?

Uncomplicated impetigo is usually self resolving in about 2–3 weeks.

Treatment can reduce this to about 10 days and reduce the risk of spread, transmission and sequelae.^1,^4,^5,¹¹ It is also important to treat any underlying skin condition such as scabies or eczema.^1,² Crusts should be removed regularly by gentle cleansing with a clean cloth before using topical treatments.^1,^3,¹⁰

Bleach in the bathwater may be useful to reduce overall skin bacteria, and to aid removal of crusts.^3,¹³ This involves using regular White King bleach 4% chlorine (non-fragranced), 12 mL for every 10 L of water, in the bathtub once daily for 10 minutes.³ UK guidelines recommend hydrogen peroxide 1% cream for localised nonbullous impetigo11; however, topical antibiotics are considered more effective,^4-6 and the use of antiseptics is not currently included in Australian guidelines.²

Mild impetigo is treated empirically with antibiotics. Skin swabs should be taken before empirical treatment is started if the impetigo is more severe or if resistance is suspected.^2,¹⁰ Non-bullous impetigo is treated with topical antibiotics if it is localised (i.e. ≤3 lesions). Oral antibiotics are used if it is more widespread, if topical treatments haven’t worked, for bullous impetigo and ecthyma, if the patient has a high risk of complications or if they have systemic symptoms.^1,^2,¹⁰

The once-daily regimen of oral trimethoprim + sulfamethoxazole is convenient for school-based administration in remote communities.² Recurrent impetigo may be associated with nasal carriage of S. aureus and decolonisation maybe indicated.²

Mupirocin 2% nasal ointment applied inside both nostrils twice a day for 5 days can be used, however, recolonisation usually recurs, and resistance can develop with prolonged or repeated use.^3,^8,^10,¹² In addition to this treatment, chlorhexidine 2% wash or soap in the shower once daily for at least 5 days, or bleach in the bathwater once daily for at least 5 days, is used.^8,¹⁰

The clinical trial that demonstrated efficacy for this approach used one quarter of a cup (approximately 60 mL) of 6% sodium hypochlorite solution per bathtub of water.^8,¹⁰

Mupirocin nasal ointment is formulated with white soft paraffin, which is less irritating to the mucous membranes than polyethylene glycol in the standard ointment.^12,^14,¹⁵

Table 1. Treatments for impetigo.

Medicine	Dose	Common adverse effects	Some potential interactions	Notes
Topical ointment, mupirocin 2%	Apply to lesions, every 8 hours for 5 days.	skin irritation	nil known	ointment only indicated
Oral dicloxacillin or flucloxacillin	Adult: 500 mg, every 6 hours for up to 7 days. Children: 12.5 mg/kg up to 500 mg, every 6 hours for up to 7 days.	diarrhoea nausea transient increase in liver enzymes and bilirubin	voriconazole probenecid warfarin
Oral, cefalexin	Adult: 500 mg every 6 hours for up to 7 days. Children: 12.5 mg/kg up to 500 mg, every 6 hours for up to 7 days	diarrhoea nausea	probenecid	Liquid form better tolerated by children than dicloxacillin or flucloxacillin Can be used if delayed non-severe penicillin hypersensitivity
Oral, cefalexin	Adult: 1 g, every 12 hours for up to 7 days. Children: 25 mg/kg up to 1 g, every 12 hours for up to 7 days.	diarrhoea nausea	probenecid
Oral, trimethoprim + sulfamethoxazole	Adult: 160 + 800 mg, every 12 hours for 3 days. Children (≥1 month old): 4+20 mg/kg up to 160 + 800 mg, every 12 hours for 3 days	fever nausea vomiting diarrhoea anorexia rash itch sore mouth hyperkalaemia thrombocytopenia	methotrexate rifampicin warfarin	Use if immediate or delayed severe penicillin hypersensitivity Use in community-associated MRSA Used in endemic settings
Oral, trimethoprim + sulfamethoxazole	Adult: 320 + 1600 mg, daily for 5 days. Children (≥1 month old): 8 + 40 mg/kg up to 320 + 1600 mg, daily for 5 days.		methotrexate rifampicin warfarin
Intramuscular, benzathine benzylpenicillin (Bicillin L-A)	Adult or child ≥20 kg: 1.2 million units (2.3 mL), as a single dose. Child 10–20 kg: 0.6 million units (1.2 mL), as a single dose Child <10 kg: 0.45 million units (0.9 mL), as a single dose	diarrhoea nausea Pain and inflammation at injection site	probenecid	Used in endemic settings Caution confusion with benzylpenicillin (BenPen) or procaine benzylpenicillin (Cilicaine)

References: Quirke¹, Therapeutic Guidelines², Gahlawat⁶, NICE¹¹, Rossi¹², GlaxoSmithKline¹⁵

Staphylococci are becoming resistant to common antibiotics.^1,^4,⁶

Resistance patterns change over time and between regions, so current local guidelines should be followed when available.4 Oral erythromycin and topical sodium fusidate are no longer recommended due to widespread resistance,^5,^10,¹⁶ and prolonged or widespread use of mupirocin causes resistance in MRSA.

It should only be used for 5 days.^2,^12,^14,¹⁶ MRSA impetigo may require different oral antibiotics guided by sensitivity testing. It has a higher prevalence among people from the Northern Territory, people in remote communities in Queensland, and Aboriginal and Torres Strait Islander and Pacific Islander peoples.^1,¹⁷

What are the preventive measures?

The risk of initial infection and subsequent spread can be reduced by maintaining good skin hygiene, washing hands regularly, and keeping fingernails short and clean.^1,^3,^5,^6,^10,¹¹ Transmission to other people can be reduced by avoiding close contact, covering affected areas with a dressing where possible, and washing hands regularly, especially after applying topical treatments to children.

Clothing, towels and bedding should be changed regularly, washed (in hot water) and dried separately from other people’s clothes and linen, and not shared.^1,^3,^5,¹⁰ Children should stay away from school, childcare facilities or kindergarten until they have been treated for at least 24 hours, and any lesions should be covered with a watertight dressing.^3,^12,¹⁸

Knowledge to practice

Impetigo is a common skin infection that is readily recognisable. Pharmacists can refer patients to their medical practitioner to receive a prescription for antibiotic treatment and give advice about the specific actions that can reduce the risk of infection and transmission.

Conclusion

Pharmacists, particularly in the community setting, can diagnose impetigo and refer patients to a medical practitioner for appropriate treatment. Pharmacists can provide advice on the effective use of antibiotics and the behavioural and environmental practices that can reduce the risk of infection and transmission.

Case Scenario Continued

Patrick’s mother returns with a prescription for mupirocin 2% ointment (to apply to lesions 3 times a day for 5 days). You explain that the crusted lesions should be gently washed away before applying the ointment, and hands washed after application.

The lesions are itchy, so you recommend that Patrick’s fingernails be trimmed to reduce the risk of scratching and spreading the infection. Patrick will need to stay away from day care until the lesions are healed, or 24 hours after treatment starts if they can be covered with a watertight dressing.

You reinforce the need for good skin hygiene for Patrick and other family members. You also recommend that she regularly change, wash and dry Patrick’s clothes, bedding and towels separately from those of the family, using heat.

Before she leaves, you invite her to contact you if the infection does not resolve within 5 days, spreads further or she notices any other symptoms.

Key points

Impetigo is a common bacterial skin infection that can be readily diagnosed in a community pharmacy.
Impetigo is highly contagious; specific behavioural and environmental practices can reduce the risk of infection and transmission.
Mild non-bullous impetigo is treated with topical antibiotics; severe and bullous impetigo is treated with oral antibiotics.
Impetigo can be endemic in remote communities and is a common complication of scabies.

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References:

Quirke K. Impetigo, DermNetNZ. 2022. At: https://dermnetnz.org/topics/impetigo
Therapeutic Guidelines. Impetigo. 2019. At: https://tgldcdp.tg.org.au/viewTopic?etgAccess=true&guidelinePage=Antibiotic&topicfile=impetigo
The Royal Children’s Hospital Melbourne. Impetigo (school sores). 2020. At: www.rch.org.au/kidsinfo/fact_sheets/Impetigo_school_sores/
Koning_S, Van der sande_R, Verhagen_AP, et al. Interventions for impetigo. Cochrane Database of Systematic Reviews. 2012. Issue 1.
Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician 2014;90(4):229–35.
Gahlawat G, Tesfaye W, Bushell M, et al. Emerging treatment strategies for impetigo in endemic and nonendemic settings: A systematic review. Clin Ther 2021;43(6)986–1006.
Welch E, Romani L, Whitfeld MJ. Recent advances in understanding and treating scabies. Fac Rev 2021;10:28.
Therapeutic Guidelines. Recurrent staphylococcal skin infection. 2019. At: https://tgldcdp.tg.org.au/viewTopic?etgAccess=true&guidelinePage=Antibiotic&topicfile=staphylococcal-skin-infection
Engelman D, Yoshizumi J, Hay RJ, et al. The 2020 International Alliance for the Control of Scabies Consensus Criteria for the Diagnosis of Scabies. Br J Dermatol 2020;183(5):808–20.
Sukumaran V, Senanayake S. Bacterial skin and soft tissue infections. Aust Prescr 2016;39:159–63.
Public Health England – National Institute for Health and Care Excellence (NICE). Impetigo: antimicrobial prescribing. 2020. At: www.nice.org.uk/guidance/ng153
Rossi S, ed. Australian Medicines Handbook online. Adelaide: Australian Medicines Handbook; 2022. At: https://amhonline.amh.net.au/
The Royal Children’s Hospital Melbourne. Skin infections – bleach baths. 2020. At: www.rch.org.au/kidsinfo/fact_sheets/skin_infections_bleach_baths/
GlaxoSmithKline Australia Pty Ltd. 2021. Australian Product Information – Bactroban (mupirocin calcium) nasal ointment. At: www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2010-PI-05303-3
GlaxoSmithKline Australia Pty Ltd. 2021. Australian Product Information – Bactroban (mupirocin calcium) cream and ointment. At: www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2010-PI-06012-3
Practical information on using antibacterial drugs. 2022. In Therapeutic Guidelines. Melbourne. Therapeutic Guidelines Ltd. At: https://tgldcdp.tg.org.au/viewTopic?etgAccess=true&guidelinePage=Antibiotic&topicfile=using-antibacterial-drugs&guidelinename=Antibiotic&sectionId=toc_d1e538#toc_d1e538
The Royal Children’s Hospital Melbourne. Cellulitis and other bacterial skin infections. 2020. At: www.rch.org.au/clinicalguide/guideline_index/Cellulitis_and_Skin_Infections/
Sansom LN, ed. Exclusion periods for infectious conditions. Australian Pharmaceutical Formulary and Handbook digital. 2022. At: https://apf.psa.org.au/health-information/exclusion-periods-infectious-conditions

BEN GILBERT, BPharm, Grad Cert Higher Education, Grad Dip Applied Science (Toxicology), MPS has experience as a community pharmacist, pharmacy owner, medication review accredited pharmacist and university lecturer and researcher. He has worked with developing countries in the Paci c region to strengthen their medical supply chain workforce and systems.