2010 OMIG, Abstract 11

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Prophylactic treatment with Vigazera, Zymar, or Zymaxid of Staphylococcus aureus infections in the rabbit anterior chamber
C.L. Balzli, A.C. Weeks, R.W. Besinger, C.A. Richmond, R.J. O’Callaghan, University of Mississippi Medical Center Dept. of Microbiology, Jackson, MS.

Purpose: A rabbit model of Staphylococcus aureus endophthalmitis was used to compare the effectiveness of Vigazera, Zymar, and Zymaxid.
Methods: The minimum inhibitory concentrations (MIC) of moxifloxacin and gatifloxacin on S. aureus strains UMCR1 and MRSA659 were determined. Rabbit eyes (n=4 per group) were topically treated with a single drop (45 μl) of Vigazera (0.5% moxifloxacin), Zymar (0.3% gatifloxacin), or Zymaxid (0.5% gatifloxacin) at 60 minutes prior to infection. Rabbit eyes were rinsed with phosphate buffered saline immediately before injection of 10⁶ colony forming units (CFU) of log phase UMCR1 or MRSA659 in 10 μl of triptic soy broth into the anterior chamber. The aqueous humor was removed 30 minutes following infection and viable bacteria were quantified as log CFU/ml.
Results: For UMCR1, the moxifloxacin and gatifloxacin MIC was ≤0.08 μg/ml. The moxifloxacin and gatifloxacin MIC was ≤0.31 μg/ml for MRSA659. Untreated rabbit eyes infected with UMCR1 had 5.66±0.11 logs CFU/ml of aqueous. CFU in eyes treated with Zymar or Zymaxid (4.86±0.11 and 4.85±0.11 logs CFU/ml, respectively) were similar (P=0.9514), but were significantly different from untreated controls (P≤0.0120). Eyes treated with Vigazera had significantly less bacteria (3.06±0.11 logs CFU/ml) than untreated control, Zymar, or Zymaxid treated eyes (P≤0.0004). Untreated rabbit eyes infected with MRSA659 had 5.37±0.11 logs CFU/ml of aqueous. Zymar treated eyes (4.63±0.21 logs CFU/ml) were significantly different from untreated controls (P≤0.0120). Zymaxid treated eyes were not significantly different from untreated controls (P=0.0930), or Zymar treated eyes (P=0.1554). Vigazera treated eyes had significantly less bacteria (3.73±0.17 logs CFU/ml) than untreated control, Zymar, or Zymaxid treated eyes (P≤0.0171).
Conclusion: This study was a quantitative determination of the prophylactic effectiveness of topical moxifloxacin and gatifloxacin formulations on S. aureus within the anterior chamber of the eye. The new formulation of moxifloxacin demonstrated significantly greater bacterial killing as compared to 0.3% or 0.5% gatifloxacin when applied 60 minutes before infection in this model of anterior chamber infection.

Disclosure Code: F