What antibiotic should be given for cellulitis caused by an insect bite?

From the Guidelines

For cellulitis caused by an insect bite, the first-line antibiotic treatment is typically cephalexin (Keflex) 500 mg orally four times daily for 5-7 days, or dicloxacillin 500 mg orally four times daily for the same duration, as recommended by the Infectious Diseases Society of America 1.

Key Considerations

• These antibiotics effectively target the most common causative organisms in cellulitis from insect bites, which are Staphylococcus aureus and Streptococcus species.
• If there is concern for methicillin-resistant Staphylococcus aureus (MRSA), consider trimethoprim-sulfamethoxazole (Bactrim) 1-2 double-strength tablets twice daily or clindamycin 300-450 mg orally four times daily.
• For patients with penicillin allergies, azithromycin 500 mg on day one followed by 250 mg daily for 4 days or clindamycin can be used.

Additional Recommendations

• While taking antibiotics, it's essential to elevate the affected area, apply warm compresses, and take over-the-counter pain relievers as needed.
• Patients should seek immediate medical attention if they develop fever, increasing pain, rapid spread of redness, or red streaking from the site, as these may indicate worsening infection requiring intravenous antibiotics.

Evidence-Based Guidelines

• The Infectious Diseases Society of America recommends empirical therapy for infection due to beta-hemolytic streptococci for outpatients with nonpurulent cellulitis 1.
• For empirical coverage of CA-MRSA in outpatients with skin and soft tissue infections, oral antibiotic options include clindamycin, trimethoprim-sulfamethoxazole, a tetracycline, and linezolid 1.

From the FDA Drug Label

Prescribing dicloxacillin sodium capsules in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

The antibiotic that should be given for cellulitis caused by an insect bite is not directly stated in the provided drug label. However, based on the information provided, dicloxacillin may be considered for the treatment of bacterial infections, including those caused by insect bites, if a bacterial infection is proven or strongly suspected.

• The drug label does not explicitly mention insect bites or cellulitis as an indication for dicloxacillin.
• It is essential to note that dicloxacillin should only be prescribed when there is a proven or strongly suspected bacterial infection 2.

From the Research

Antibiotic Treatment for Cellulitis Caused by Insect Bites

• The majority of cases of cellulitis are nonculturable, and therefore, the causative bacteria are unknown 3.
• In cases where organisms are identified, most are due to β-hemolytic Streptococcus and Staphylococcus aureus 3.
• Treatment of primary and recurrent cellulitis should initially cover Streptococcus and methicillin-sensitive S. aureus, with expansion for methicillin-resistant S. aureus (MRSA) in cases of cellulitis associated with specific risk factors 3.

Recommended Antibiotics

• Cephalexin is a commonly prescribed antibiotic for the treatment of uncomplicated cellulitis 4, 5.
• Trimethoprim-sulfamethoxazole has been shown to have a higher treatment success rate than cephalexin for empiric therapy of cellulitis 5.
• Clindamycin is also effective in treating cellulitis, especially in cases with moderately severe symptoms or in obese patients 5.
• Levofloxacin has been shown to be effective in treating uncomplicated cellulitis, with a 5-day course being as effective as a 10-day course 6.

Duration of Treatment

• Five days of treatment is sufficient, with extension if symptoms are not improved 3.
• A study comparing short-course (5 days) and standard (10 days) treatment for uncomplicated cellulitis found no significant difference in clinical outcome between the two courses of therapy 6.

Additional Considerations

• The addition of an oral anti-inflammatory agent to antibiotic treatment has been shown to hasten the resolution of cellulitis-related inflammation 7.
• Factors associated with treatment failure include therapy with an antibiotic that is not active against community-associated MRSA and severity of cellulitis 5.