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 bullous and nonbullous cases, as this approach has been shown to be effective in managing the infection. The treatment of impetigo depends on the severity and extent of the infection, with topical antimicrobials being suitable for limited cases and oral therapy recommended for patients with numerous lesions or in outbreaks affecting several people to help decrease transmission of infection 1.

Key Considerations

• Gram stain and culture of the pus or exudates from skin lesions can help identify the cause of the infection, but treatment without these studies is reasonable in typical cases 1.
• Oral therapy for ecthyma or impetigo should be a 7-day regimen with an agent active against S. aureus, such as dicloxacillin or cephalexin, unless cultures yield streptococci alone, in which case oral penicillin is recommended 1.
• When MRSA is suspected or confirmed, alternative antibiotics like doxycycline, clindamycin, or sulfamethoxazole-trimethoprim (SMX-TMP) should be used 1.

Prevention and Management

• Washing the affected areas gently with soap and water before applying medication can help remove crusts and improve treatment effectiveness.
• Preventing the spread of impetigo involves avoiding touching or scratching the sores, using separate towels and washcloths, and washing hands frequently.
• Impetigo is a highly contagious infection caused primarily by Staphylococcus aureus or Streptococcus pyogenes bacteria, which enter through breaks in the skin 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. 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 of 71% and 93% in two studies 2. Key points are:

• Mupirocin ointment has a high pathogen eradication rate of 94% and 100% in the two studies 2.
• The indication for mupirocin ointment, 2% is for the topical treatment of impetigo due to Staphylococcus aureus and Streptococcus pyogenes 2.

From the Research

Definition and Types of Impetigo

• Impetigo is a highly contagious, superficial skin infection that most commonly affects children two to five years of age 3, 4.
• There are two principal types of impetigo: nonbullous (70% of cases) and bullous (30% of cases) 3.
• Nonbullous impetigo, or impetigo contagiosa, is caused by Staphylococcus aureus or Streptococcus pyogenes, and is characterized by honey-colored crusts on the face and extremities 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

• Topical antibiotics such as mupirocin, retapamulin, and fusidic acid are effective treatments for impetigo 3, 4, 5, 6.
• Oral antibiotic therapy can be used for impetigo with large bullae or when topical therapy is impractical 3, 7.
• Amoxicillin/clavulanate, dicloxacillin, cephalexin, clindamycin, doxycycline, minocycline, trimethoprim/sulfamethoxazole, and macrolides are options for oral antibiotic therapy 3, 7.
• Penicillin is not a recommended treatment option due to its low efficacy 7, 5.
• Natural therapies such as tea tree oil, olive, garlic, and coconut oils, and Manuka honey have been anecdotally successful, but lack sufficient evidence to recommend or dismiss them as treatment options 3.

Comparison of Treatment Options

• Topical mupirocin and fusidic acid have been shown to be equally effective, or more effective, than oral treatment 5, 6.
• Retapamulin is an effective alternative, but may entail higher cost 6.
• Ozenoxacin is a topical quinolone that has been shown to be effective in treating impetigo 3, 6.
• Disinfectant solutions are not useful in the treatment of impetigo 3, 5.

Resistance and Safety

• Bacteria causing impetigo show growing resistance rates for commonly used antibiotics 5.
• Mupirocin has shown clinical efficacy against MRSA, but a bacterial culture is recommended to rule out resistance 6.
• Retapamulin is indicated for lesions of impetigo that are colonized by MSSA and streptococcus S. pyogenes, but not MRSA 6.
• Adverse events associated with topical antibiotics are minimal, with the most common being pruritus at the application site 6.