From the Guidelines
For cellulitis treatment, a 5- to 6-day course of antibiotics active against streptococci is recommended, particularly for patients able to self-monitor and who have close follow-up with primary care. This approach is supported by the most recent guidelines, including the 2021 American College of Physicians' best practice advice 1. The choice of antibiotic should be based on the severity of the infection, local resistance patterns, and patient factors such as allergies and comorbidities.
Key Considerations
- For mild to moderate infections, cephalexin 500 mg orally four times daily or dicloxacillin 500 mg orally four times daily can be used 1.
- For patients with penicillin allergy, clindamycin 300-450 mg orally three times daily is a suitable alternative 1.
- For more severe infections or those with suspected MRSA, vancomycin 15-20 mg/kg every 8-12 hours or other antimicrobials effective against both MRSA and streptococci should be considered 1.
- Treatment duration should be extended if the infection has not improved within the initial 5-6 days, and elevation of the affected area, warm compresses, and pain management are important adjunctive measures 1.
Special Cases
- Patients with penetrating trauma, evidence of MRSA infection elsewhere, nasal colonization with MRSA, injection drug use, or systemic inflammatory response syndrome (SIRS) may require broader antibiotic coverage, including vancomycin or other antimicrobials effective against MRSA and streptococci 1.
- Immunocompromised patients or those with complicated cases may require longer treatment durations, typically 10-14 days 1.
From the Research
Antibiotics Dosing for Cellulitis
- The majority of non-purulent, uncomplicated cases of cellulitis are caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus, and appropriate targeted coverage of this pathogen with oral antibiotics such as penicillin, amoxicillin, and cephalexin is sufficient 2.
- Even with rising rates of community-acquired methicillin-resistant Staphylococcus aureus, coverage for non-purulent cellulitis is generally not recommended 2.
- Trimethoprim-sulfamethoxazole and clindamycin are preferred empiric therapy for outpatients with cellulitis in the community-associated MRSA-prevalent setting 3.
- Cephalexin remains a cost-effective therapy for outpatient management of cellulitis at current estimated MRSA levels, but clindamycin becomes more cost-effective at high likelihoods of MRSA infection 4.
- There is no evidence to support the superiority of any one antibiotic over another for the treatment of cellulitis, and antibiotics with activity against methicillin-resistant Staphylococcus aureus do not add an advantage 5.
- The use of intravenous antibiotics over oral antibiotics and treatment duration of longer than 5 days are not supported by evidence 5.
Factors Affecting Treatment
- The probability of infection due to MRSA and the severity of cellulitis are factors that can affect the choice of antibiotic therapy 3, 4.
- The cost of antibiotics, such as linezolid, can also influence the choice of therapy 4.
- Patient factors, such as obesity, can also affect the success of treatment 3.