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doi: 10.1097/ICO.0b013e318268d6f4
Clinical Science

In Vitro Comparison of Combination and Monotherapy for the Empiric and Optimal Coverage of Bacterial Keratitis Based on Incidence of Infection

Kowalski, Regis P. MS, [M]ASCP; Kowalski, Tyler A.; Shanks, Robert M. Q. PhD; Romanowski, Eric G. MS; Karenchak, Lisa M. BS; Mah, Francis S. MD

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Purpose: Cefazolin/tobramycin, cefuroxime/gentamicin, and moxifloxacin were compared using bacterial keratitis isolates to determine whether empiric therapy constituted optimal antibacterial 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 minimum inhibitory concentrations 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 S. aureus was best covered by gentamicin 100% (9 of 9). Tobramycin was more potent (P = 0.00001) than gentamicin for P. aeruginosa, whereas cefazolin was more potent (P = 0.0004) than cefuroxime for S. aureus.

Conclusions: Although there seems 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.

© 2013 by Lippincott Williams & Wilkins.


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