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2007 OMIG, Abstract 11

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Fluoroquinolone Prophylaxis for Experimental MRSA Keratitis in a LASIK Model
C McCormick1, C Balzli1, A Caballero1, A Tang1, B Huang2, and R O’Callaghan1
University of Mississippi Medical Center, Jackson, MS, USA Department of Microbiology1, Department of Ophthalmology2

Purpose:To determine the effectiveness of prophylactic fluoroquinolone therapy in a unique rabbit model of experimental methicillin-resistant Staphylococcus aureus (MRSA) LASIK keratitis.
To simulate clinical use, a single topical drop of either Vigamox (0.5% moxifloxacin) or Zymar (0.3% gatifloxacin, 0.005% benzalkonium chloride) was administered to rabbit eyes (n = 8 eyes per group) at 16 and 15 minutes prior to infection. LASIK surgery was performed to create a corneal flap and MRSA strain 91169 (500 colony forming units [CFU]) was topically administered within the flap. At 5 hours postinfection (PI), corneas were harvested, homogenized, and serially diluted. Aliquots (100µl) were plated in triplicate and incubated at 37oC overnight. Data are presented in log10 CFU ± SEM.
Untreated rabbit corneas (n = 8) infected with MRSA yielded approximately 5.14 ± 0.047 logs of bacteria. Rabbits treated with Vigamox contained 1.30 ± 0.422 logs of bacteria and corneas treated with Zymar had 3.79 ± 0.382 logs of bacteria. Both Vigamox and Zymar treated eyes had significantly fewer bacteria when compared to untreated eyes (P < 0.0001 and P = 0.0096, respectively). Furthermore, Vigamox treated eyes yielded significantly fewer bacteria than Zymar treated eyes (P = 0.0006).
Conclusions:In a prophylactic model of MRSA-associated LASIK keratitis, both products were effective compared to the control. Vigamox was shown to be significantly better than Zymar.

Financial support was provided by Alcon Laboratories, Fort Worth, TX.


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