Which antibiotic is commonly used for MSSA eyelid infections?

• A. Doxycycline
• B. Augmentin
• C. Dicloxacillin
• D. Ceftriaxone

Answer: (C)

When treating eyelid infections caused by methicillin-susceptible Staphylococcus aureus, the best choice is an antibiotic that is specifically active against MSSA and suitable for outpatient use. Dicloxacillin fits this role as an anti-staphylococcal penicillin that resists staphylococcal penicillinases, effectively blocking bacterial cell wall synthesis in MSSA. It has a long history of reliably treating skin and soft tissue infections, including lids, with good tolerability and convenient dosing.

Doxycycline can cover a broader spectrum, including some MSSA and MRSA, and is useful for lid irritations or blepharitis, but it isn’t the first-line agent for a straightforward MSSA eyelid infection because of its slower bactericidal action and potential side effects like photosensitivity and antibiotic restrictions in certain populations. Augmentin adds clavulanate to amoxicillin, broadening coverage to beta-lactamase–producing organisms and some oral anaerobes; this broader spectrum isn’t necessary for a simple MSSA eyelid infection and isn’t as targeted as a dedicated anti-staphylococcal penicillin. Ceftriaxone is an intravenous drug used for more serious systemic infections and isn’t appropriate for a localized, uncomplicated eyelid infection.