Purpose Cefazolin/tobramycin, Cefuroxime/gentamicin, and moxifloxacin were compared using bacterial keratitis isolates to determine whether empiric therapy constituted optimal anti-bacterial treatment. Methods Based on percent incidence of corneal infection, 27 Staphylococcus aureus, 16 Pseudomonas aeruginosa, 10 Serratia marcescens, 4 Moraxella lacunata, 3 Haemophilus influenzae, 9 coagulase-negative Staphylococci, 7 Streptococcus viridans, 6 Streptococcus pneumoniae, 7 assorted Gram-positive isolates, and 11 assorted Gram-negative isolates were tested for MICs to cefazolin, tobramycin, cefuroxime, gentamicin, and moxifloxacin using E-tests to determine susceptibility and potency. Results The in vitro coverage (susceptible to at least one antibiotic) of cefuroxime/gentamicin (97%) was statistically equal to cefazolin/tobramycin (93%) and moxifloxacin (92%) (p=0.29). Double coverage (susceptible to both antibiotics) was equivalent (p=0.77) for cefuroxime/ gentamicin (42%) and cefazolin/tobramycin (40%). The susceptibilities of individual coverage were moxifloxacin (92%), gentamicin (89%), tobramycin (74%), cefazolin (58%), and cefuroxime (52%). Methicillin-resistant Staphylococcus aureus was best covered by gentamicin 100% (9 of 9). Tobramycin was more potent (p=0.00001) than gentamicin for Pseudomonas aeruginosa, while cefazolin was more potent (p=0.0004) than cefuroxime for Staphylococcus aureus. Conclusions Although there appears to be no in vitro empiric coverage advantage between cefazolin/tobramycin, cefuroxime/gentamicin, and moxifloxacin monotherapy, potency differences may occur, and optimal treatment can best be determined with laboratory studies.

Tigecycline is a potential candidate for a topical ocular antibiotic.