What is the recommended treatment, duration, and antibiotics of choice for a patient with Bullous Impetigo, considering factors such as underlying conditions like diabetes or immunosuppression?

Treatment of Bullous Impetigo

First-Line Antibiotic Selection

For bullous impetigo, oral cephalexin 25-50 mg/kg/day divided into 4 doses (or 250-500 mg four times daily in adults) for 7 days is the recommended first-line treatment, as bullous impetigo is exclusively caused by toxin-producing Staphylococcus aureus and requires systemic therapy. 1, 2

Why Systemic Therapy is Required

• Bullous impetigo is caused exclusively by toxin-producing S. aureus that produces exfoliative toxins, resulting in large, flaccid bullae that typically affect intertriginous areas 1, 3, 4
• Unlike non-bullous impetigo where topical therapy may suffice for limited disease, bullous impetigo requires oral antibiotics due to the systemic nature of toxin production 1, 3
• The bullae formation indicates deeper involvement than the superficial crusting seen in non-bullous impetigo 3, 4

Specific Antibiotic Regimens

First-Line Options for Presumed MSSA

• Cephalexin: 25-50 mg/kg/day divided into 4 doses for children (or 250-500 mg four times daily for adults) for 7 days 1, 2
• Dicloxacillin: 25-50 mg/kg/day divided into 4 doses for children (or 250 mg four times daily for adults) for 7 days 1, 2
• Cephalexin given twice daily has been shown equally effective as dicloxacillin given four times daily in a randomized controlled trial of 70 patients with staphylococcal bullous impetigo, with the advantage of improved compliance 2

Alternative Options When MRSA is Suspected

• Clindamycin: 20-30 mg/kg/day divided into 3 doses for children (or 300-450 mg three times daily for adults) for 7 days 1
• Sulfamethoxazole-trimethoprim (SMX-TMP): 8-12 mg/kg/day (based on trimethoprim component) divided into 2 doses for 7 days 1
• Doxycycline: Only for children over 8 years old at 2-4 mg/kg/day divided into 2 doses for 7 days, due to risk of permanent dental staining in younger children 1

When to Suspect MRSA

• In areas with high community MRSA prevalence, empiric therapy should cover MRSA until culture results are available 1
• Consider MRSA coverage if the patient fails initial therapy with beta-lactam antibiotics 1

Treatment Duration

The standard duration for oral antibiotic therapy is 7 days, not the shorter 5-day course used for topical agents in non-bullous impetigo. 1, 5

• Treatment failures and delayed healing are more common when shorter courses are used 2
• Recurrences occurred in 3 patients in each treatment group in the cephalexin vs. dicloxacillin trial, all limited to patients with bullous impetigo, emphasizing the need for adequate treatment duration 2

Antibiotics to Avoid

• Penicillin alone is seldom effective and should only be used when cultures confirm streptococci alone, which does not occur in bullous impetigo since it is exclusively staphylococcal 1
• Amoxicillin alone should not be used because it lacks adequate coverage against S. aureus 1
• Topical therapy alone (such as mupirocin) is inadequate for bullous impetigo, unlike non-bullous impetigo where it may be first-line for limited disease 1, 6

Special Populations

Patients with Diabetes or Immunosuppression

• These patients may have more severe or spreading lesions requiring systemic antibiotics 5
• Consider lower threshold for hospital admission if extensive disease or systemic signs are present 7
• Monitor closely for treatment failure and consider culture-directed therapy earlier 1

Pregnant Patients

• Cephalexin can be considered a safe alternative for pregnant patients 1
• Avoid tetracyclines (doxycycline) due to risk of dental staining in the fetus 1

Patients with Penicillin Allergy

• Clindamycin is the preferred alternative for patients with penicillin allergy 1
• Macrolides can be used, though resistance rates to erythromycin are rising 1, 8

Adjunctive Measures

Local Wound Care

• Keep lesions covered with clean, dry bandages to prevent spread 1
• Apply plain petrolatum ointment and bandages over any open erosions after bullae have deroofed 7

Infection Control

• Maintain good personal hygiene with regular handwashing 1
• Avoid sharing personal items that contact the skin 1
• Clean high-touch surfaces that contact bare skin 1

When to Obtain Cultures

• Gram stain and culture of pus or exudates are recommended to identify the causative organism, particularly in areas with high MRSA prevalence 1
• Culture is especially important in patients with diabetes or immunosuppression who may be at higher risk for resistant organisms 1
• Treatment without cultures is reasonable in typical cases, but empiric therapy should cover MRSA in high-prevalence areas 1

Monitoring and Follow-Up

• Patients should be re-evaluated if there is no improvement after 48-72 hours of therapy 9
• Clinical response is typically evident within the first week, with clearing of lesions 2
• Delayed healing with persistence of staphylococci in lesions may occur and warrants culture and possible antibiotic adjustment 2

Common Pitfalls to Avoid

• Do not use topical therapy alone for bullous impetigo, as it requires systemic antibiotics due to toxin-mediated pathogenesis 1, 3
• Do not prescribe penicillin or amoxicillin alone, as nearly all staphylococcal strains causing bullous impetigo are resistant 1, 2
• Do not use treatment courses shorter than 7 days, as this increases risk of treatment failure and recurrence 1, 5
• Do not use disinfectant solutions as primary therapy, as there is little evidence they improve outcomes 1