May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Killing Potential of Ocular Antibiotic Combinations Against Methicillin-Resistant Staphylococci
Author Affiliations & Notes
  • B. D. Novosad
    Dept of Ophthalmology, University of Oklahoma Health Sciences Ctr, Oklahoma City, Oklahoma
  • M. C. Callegan
    Dept of Ophthalmology, University of Oklahoma Health Sciences Ctr, Oklahoma City, Oklahoma
    Molecular Pathogenesis of Eye Infections Research Center, Dean McGee Eye Institute, Oklahoma City, Oklahoma
  • Footnotes
    Commercial Relationships B.D. Novosad, None; M.C. Callegan, Allergan Inc., C.
  • Footnotes
    Support NIH grant R01EY12985 and Lew R. Wasserman Award from Research to Prevent Blindness, Inc. (to MCC) and an unrestricted research grant from Allergan Inc.
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 4747. doi:
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    • Get Citation

      B. D. Novosad, M. C. Callegan; Killing Potential of Ocular Antibiotic Combinations Against Methicillin-Resistant Staphylococci. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4747.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose:: Vancomycin and cefuroxime are two of the most commonly used antibiotics for intracameral injection during cataract extraction for endophthalmitis prophylaxis. This study was designed to evaluate the potential antimicrobial synergism/additivity of gatifloxacin in combination with vancomycin or cefuroxime against methicillin resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE).

Methods:: Gatifloxacin (GAT) powder in combination with vancomycin (VAN) or cefuroxime (CEF) was tested against endophthalmitis isolates of MRSA and MRSE, Before testing antibiotic combinations, MICs of each antibiotic were determined for all isolates. Antibiotic combinations tested included final concentrations of 0.06-4 times the MIC determined for each antibiotic. Using checkerboard analysis, isolates were cultured in appropriate medium to a concentration equivalent to a 0.5 McFarland standard and placed into wells of microtiter plates with an equal volume of antibiotic combination. Plates were incubated for 24 hours at 37oC and absorbance was determined at OD650. The potential synergism for each antibiotic combination was determined by calculating the fractional inhibitory concentration (FIC) index for each strain.

Results:: Synergy or additivity was observed with the antibiotic combination of GAT/VAN in 67% of MRSA and 80% of MRSE. Partial synergy or additivity was observed with the antibiotic combination of GAT/CEF in 44% of MRSA and 40% of MRSE.

Conclusions:: The GAT/VAN combination appeared to have greater synergistic tendencies against MRSA and MRSE endophthalmitis isolates than the GAT/CEF combination.

Keywords: bacterial disease • endophthalmitis • antibiotics/antifungals/antiparasitics 
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