Which antibiotic provides Gram-negative coverage for ocular infections?

• A. Gentamicin
• B. Cefazolin
• C. Erythromycin
• D. Penicillin

Answer: (A)

The question tests understanding of antibiotic spectra relevant to eye infections, specifically which drug targets Gram-negative bacteria. Gentamicin is an aminoglycoside with strong activity against Gram-negative organisms commonly implicated in ocular infections, including Pseudomonas aeruginosa. It is commonly used topically for conditions like keratitis and conjunctivitis because it reaches the ocular surface effectively when applied as drops or ointment.

Mechanistically, gentamicin binds the 30S ribosomal subunit, causing misreading of mRNA and ultimately bacterial death. This Gram-negative targeting is what makes it the best choice for infections where Pseudomonas and other Gram-negative bacteria are a concern.

The other options are more oriented toward Gram-positive pathogens or have only limited Gram-negative activity, so they’re less suitable when Gram-negative coverage is required.