Treatment of Cellulitis from Bug Bites

Antibiotic Selection

The American College of Physicians and the Infectious Diseases Society of America recommend using an antibiotic active against streptococci, such as penicillin, amoxicillin, amoxicillin-clavulanate, dicloxacillin, or clindamycin, as the first-line treatment for cellulitis resulting from a bug bite, with a strength of evidence rated as strong 1, 2
For typical non-purulent cellulitis without systemic signs of infection, the Infectious Diseases Society of America suggests using an antibiotic active against streptococci, with suitable oral antibiotics including penicillin 3, amoxicillin-clavulanate 1, and clindamycin [1, 3] [2, 4]
Consider MRSA coverage if the cellulitis is associated with penetrating trauma, evidence of MRSA infection elsewhere, nasal colonization with MRSA, injection drug use, purulent drainage, or systemic inflammatory response syndrome (SIRS), according to the Infectious Diseases Society of America 4, 5

A 5-day course of antimicrobial therapy is as effective as a 10-day course if clinical improvement has occurred by day 5, with a moderate strength of evidence 1, 3
Treatment should be extended if the infection has not improved within 5 days, as recommended by the Infectious Diseases Society of America 3

Elevation of the affected area to hasten improvement by promoting gravity drainage of edema and inflammatory substances is recommended by the Infectious Diseases Society of America 1
Treatment of predisposing conditions, such as tinea pedis, trauma, or venous eczema, is suggested by the Infectious Diseases Society of America 1
In lower extremity cellulitis, careful examination of interdigital toe spaces to treat fissuring, scaling, or maceration that may harbor pathogens is recommended by the Infectious Diseases Society of America 3

Blood cultures are not routinely recommended for typical cases of cellulitis, but should be obtained for patients with malignancy, severe systemic features, unusual predisposing factors, or immunocompromise, according to the Infectious Diseases Society of America 1, 4
Systemic corticosteroids could be considered in non-diabetic adult patients with cellulitis to reduce inflammation, with a low strength of evidence 1, 3

For mild cellulitis without systemic signs, the Infectious Diseases Society of America recommends first-line treatment with cephalexin 500 mg orally four times daily for 5 days, or clindamycin 300-450 mg orally four times daily for 5 days if penicillin-allergic 1, 3
For cellulitis with systemic signs or from bug bites, consider combination therapy with a beta-lactam plus either trimethoprim-sulfamethoxazole or doxycycline, as suggested by the Infectious Diseases Society of America 5

Patients should show clinical improvement within 24-48 hours of starting appropriate antibiotics, and consider outpatient treatment for patients without SIRS, altered mental status, or hemodynamic instability, according to the Infectious Diseases Society of America 3
Hospitalization is recommended if there is concern for deeper or necrotizing infection, poor adherence to therapy, severe immunocompromise, or if outpatient treatment is failing, as recommended by the Infectious Diseases Society of America 3

Elevation of the affected area to promote gravity drainage of edema and inflammatory substances, as well as treatment of predisposing conditions such as tinea pedis, venous eczema, and trauma or other skin conditions, is recommended by the Infectious Diseases Society of America 6
Systemic corticosteroids could be considered in non-diabetic adult patients with cellulitis to reduce inflammation, according to the Clinical Infectious Diseases guidelines 6

Each attack of cellulitis causes lymphatic inflammation and possibly permanent damage, and severe or repeated episodes may lead to lymphedema, as stated by the Clinical Infectious Diseases guidelines 6
Measures to reduce recurrences include treating interdigital maceration, keeping skin well hydrated with emollients, and reducing underlying edema through elevation, compression stockings, or diuretic therapy if appropriate, as recommended by the Infectious Diseases Society of America 6
For frequent infections despite preventive measures, prophylactic antibiotics may be reasonable, with options including monthly intramuscular benzathine penicillin injections or oral therapy with twice-daily doses of either erythromycin or penicillin V, according to the Clinical Infectious Diseases guidelines 6