What is the diagnosis and treatment for impetigo?

From the Guidelines

Impetigo should be treated with either topical mupirocin or retapamulin twice daily for 5 days for mild cases, while oral therapy with an agent active against S. aureus, such as dicloxacillin or cephalexin, is recommended for more extensive infections or outbreaks. The treatment of impetigo depends on the severity and extent of the infection, as well as the presence of any underlying conditions or allergies 1.

Key Considerations

• For mild cases of impetigo, topical antimicrobials such as mupirocin or retapamulin are effective and can be applied twice daily for 5 days 1.
• For more extensive infections or outbreaks, oral antibiotics such as dicloxacillin or cephalexin are recommended, with a 7-day regimen 1.
• In cases where MRSA is suspected or confirmed, alternative antibiotics such as doxycycline, clindamycin, or sulfamethoxazole-trimethoprim may be used 1.

Management and Prevention

• Keeping the affected areas clean by gently washing with soap and water can help prevent the spread of infection.
• Avoiding scratching and covering lesions if possible can also help prevent transmission to others.
• Good hygiene practices, including regular handwashing and not sharing personal items, are essential in preventing transmission to others and recurrence.

Important Notes

• Impetigo is a highly contagious infection caused primarily by Staphylococcus aureus or Streptococcus pyogenes bacteria that enter through breaks in the skin.
• The infection typically presents as honey-colored crusts, red sores, or fluid-filled blisters that rupture and form yellow crusts.
• Prompt treatment with antibiotics and good hygiene practices can help prevent complications and reduce the risk of transmission to others 1.

From the FDA Drug Label

The efficacy of topical mupirocin ointment in impetigo was tested in two studies. CLINICAL STUDIES In the first, patients with impetigo were randomized to receive either mupirocin ointment or vehicle placebo t.i. d. for 8 to 12 days. Clinical efficacy rates at end of therapy in the evaluable populations (adults and pediatric patients included) were 71% for mupirocin ointment (n=49) and 35% for vehicle placebo (n=51). Pathogen eradication rates in the evaluable populations were 94% for mupirocin ointment and 62% for vehicle placebo There were no side effects reported in the group receiving mupirocin ointment. In the second study, patients with impetigo were randomized to receive either mupirocin ointment t.i. d. or 30 to 40 mg/kg oral erythromycin ethylsuccinate per day (this was an unblinded study) for 8 days. There was a follow-up visit 1 week after treatment ended. Clinical efficacy rates at the follow-up visit in the evaluable populations (adults and pediatric patients included) were 93% for mupirocin ointment (n=29) and 78. 5% for erythromycin (n=28). Pathogen eradication rates in the evaluable patient populations were 100% for both test groups. There were no side effects reported in the mupirocin ointment group. Pediatrics There were 91 pediatric patients aged 2 months to 15 years in the first study described above Clinical efficacy rates at end of therapy in the evaluable populations were 78% for mupirocin ointment (n=42) and 36% for vehicle placebo (n=49). In the second study described above, all patients were pediatric except two adults in the group receiving mupirocin ointment. The age range of the pediatric patients was 7 months to 13 years The clinical efficacy rate for mupirocin ointment (n=27) was 96%, and for erythromycin it was unchanged (78.5%). Mupirocin ointment, 2% is indicated for the topical treatment of impetigo due to: Staphylococcus aureus and Streptococcus pyogenes.

Mupirocin ointment is effective in the treatment of impetigo due to Staphylococcus aureus and Streptococcus pyogenes, with clinical efficacy rates ranging from 71% to 96% in different studies 2. Key points about mupirocin ointment for impetigo include:

• Indication: Topical treatment of impetigo due to Staphylococcus aureus and Streptococcus pyogenes 2
• Clinical efficacy rates: 71% to 96% in different studies 2
• Pathogen eradication rates: 94% to 100% in different studies 2
• Pediatric use: Mupirocin ointment is effective in pediatric patients, with clinical efficacy rates ranging from 78% to 96% 2

From the Research

Definition and Types of Impetigo

• Impetigo is the most common bacterial skin infection in children two to five years of age 3
• There are two principal types: nonbullous (70% of cases) and bullous (30% of cases) 3
• Nonbullous impetigo, or impetigo contagiosa, is caused by Staphylococcus aureus or Streptococcus pyogenes 3
• Bullous impetigo, which is caused exclusively by S. aureus, results in large, flaccid bullae and is more likely to affect intertriginous areas 3

Treatment Options

• Treatment includes topical antibiotics such as mupirocin, retapamulin, and fusidic acid 3
• Oral antibiotic therapy can be used for impetigo with large bullae or when topical therapy is impractical 3
• Amoxicillin/clavulanate, dicloxacillin, cephalexin, clindamycin, doxycycline, minocycline, trimethoprim/sulfamethoxazole, and macrolides are options, but penicillin is not 3
• Topical mupirocin was shown to be slightly superior to oral erythromycin 4
• Fusidic acid and mupirocin are of similar efficacy 4
• Penicillin was not as effective as most other antibiotics 4

Efficacy and Safety of Topical Antibiotics

• Topical antibiotics had greater resolution of impetigo in comparison to vehicle in clinical trials 5
• Adverse events were minimal, with the most common being pruritus at the application site 5
• Mupirocin ointment had the lowest cost among topical antibiotics 5
• Mupirocin has shown clinical efficacy against MRSA but a bacterial culture is recommended to rule out resistance 5
• Ozenoxacin and retapamulin are effective alternatives but may entail higher cost 5

Resistance and Treatment Considerations

• Empiric treatment considerations have changed with the increasing prevalence of antibiotic-resistant bacteria 3
• Methicillin-resistant S. aureus, macrolide-resistant streptococcus, and mupirocin-resistant streptococcus have been documented 3
• Fusidic acid, mupirocin, and retapamulin cover methicillin-susceptible S. aureus and streptococcal infections 3
• Clindamycin proves helpful in suspected methicillin-resistant S. aureus infections 3
• Trimethoprim/sulfamethoxazole covers methicillin-resistant S. aureus infection, but is inadequate for streptococcal infection 3