An in vitro comparison of the susceptibilities of bacterial isolates from patients with conjunctivitis and blepharitis to newer and established topical antibiotics

This retrospective study compared new and established topical antibiotics with regard to the in vitro susceptibility of bacterial isolates recovered from patients with con junctivitis (n = 385) and blepharitis (n = 173) using the National Committee for Clinical Laboratory Standards approved disk diffusion method. The percent susceptibility of recovered isolates to single antibiotic agents or combinations were ranked from greatest to least: chloramphenicol, bacitracin/polymyxin B, ofloxacin, sulfa, ciprofloxacin, trimethoprim/polymyxin B, norfloxacin, gentamicin, bacitracin, trimethoprim, tobramycin, neomycin, erythromycin, and polymyxin B. We determined that none of the available topical antibiotics provided 100% broad spectrum coverage in vitro. Established antibiotics often provided coverage comparable to the newer drugs. Due to the unproven value of in vitro testing as a predictor of clinical outcome in bacterial blepharitis and conjunctivitis, the ophthalmologist should choose therapy based on clinical experience, ongoing critical evaluation of available antibiotics, and cost-effectiveness.