Purchase this article with an account.
F.S. Mah, E.G. Romanowski, K.A. Yates, R.P. Kowalski, Y.J. Gordon; Comparison of a New Topical Fluoroquinolone, Gatifloxacin (ZymarTM), with Levofloxacin (QixinTM) and Ciprofloxacin (CiloxanTM) in the Treatment of Fluoroquinolone–Resistant Staphylococcus aureus Keratitis in a NZW Rabbit Model. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4982.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose:It is generally believed that in vitro resistance does not always correlate with in vivo efficacy in topical ocular therapy. In this study, we determined whether gatifloxacin–resistant S. aureus (Gat–R–Sa) keratitis could be successfully treated with topical 0.3% gatifloxacin (GAT) (ZymarTM) in an animal model and compared the results to other commercially available topical fluoroquinolones, 0.3% ciprofloxacin (CIP)(CiloxanTM) and 0.5% levofloxacin (LEV)(QuixinTM).Methods: Two clinical isolates of Gat–R–Sa, with MICs of 12 µg/ml (a MRSA isolate) and 64 µg/ml (a MSSA isolate) to gatifloxacin, were used in separate experiments. Each consisted of 4 treatment groups of 6 animals (GAT, 0.5% levofloxacin [QuixinTM], 0.3% ciprofloxacin [Ciloxan®], and Saline) and a baseline (onset of therapy) colony count control group. Rabbits were infected intrastromally with 2 X 103 cfu in both eyes. Topical therapy began 4 hours PI every 15 minutes for 5 hours (21 doses). After therapy, the eyes were graded for clinical signs of infection. Subsequently, the corneas were homogenized to determine a viable bacterial count. The clinical and the colony count data were analyzed with non–parametric and continuous statistical methods.Results:In the treatment of Gat–R–Sa (MIC of 12 µg/ml – the MRSA isolate), GAT demonstrated a significantly lower clinical corneal infiltrate score compared with all other groups and demonstrated a bactericidal 3.8–log decrease in colony counts compared with the baseline colony count and a 5.9–log decrease in colony counts compared with the Saline control. For Gat–R–Sa (MIC of 64 µg/ml – the MSSA isolate), GAT demonstrated significantly lower overall ocular scores compared with all other groups and demonstrated a 2.7 log decrease in colony counts compared with the baseline colony count and a 5.1–log decrease in colony counts compared with the Saline control. For both isolates, GAT demonstrated a significantly greater decrease in colony counts compared to all other treatment groups. Conclusion: We demonstrated "Proof of Principle" that in vitro antibiotic resistance does not always correlate with in vivo antibiotic resistance. An aggressive treatment regimen with GAT appears to overcome in vitro resistance resulting in the successful treatment of Fluoroquinolone–Resistant Staphylococcus aureus infection in the NZW rabbit keratitis model.
This PDF is available to Subscribers Only