Non-purulent cellulitis is typically treated with which class of antibiotics, and when is MRSA coverage indicated?

• A. Vancomycin alone.
• B. Macrolide antibiotics.
• C. Fluoroquinolones.
• D. Beta-lactams; MRSA coverage added if purulence, risk factors, systemic signs, or high local MRSA prevalence.

Answer: (D)

Non-purulent cellulitis is usually caused by streptococci, so a beta-lactam antibiotic that effectively covers streptococci is the typical first-line choice. MRSA coverage is not routine and is added only when there are signs that MRSA could be involved or the infection is more severe. Purulence or fluctuance points to Staphylococcus aureus (potentially MRSA), so adding MRSA-active coverage makes sense in that setting. Other factors that tilt toward MRSA coverage include risk factors for MRSA (such as known colonization or recent MRSA infection), systemic signs of illness (fever or a more toxic appearance), and a high local prevalence of MRSA. If none of these MRSA-indicating features are present, a narrow-spectrum beta-lactam alone remains appropriate because it targets the typical organisms while avoiding unnecessary broad coverage.