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JJ Dajcs, BA Thibodeaux, DO Girgis, M Traidej, RJ O'Callaghan, DW Stroman, BA Schlech, N Carreras, JA Vallet; The Effectiveness of Fluoroquinolone Antibiotics Administered Prophylactically for Staphylococcus Aureus Keratitis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1583.
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Purpose: To compare the effectiveness of standard and experimental formulations of fluoroquinolone antibiotics in a prophylactic model of S. aureus keratitis. Methods: S. aureus strain 8325-4 was grown to log phase, diluted to approximately 500 colony forming units (CFU) per 10 µl, and injected intrastromally into rabbit corneas (N ≥ 6 per group). Antibiotic formulations analyzed included Moxifloxacin (0.5%), CILOXAN (0.3% ciprofloxacin), Ciprofloxacin HPMC (0.3% ciprofloxacin in 3.3% hydroxypropyl-methylcellulose), and Ciprofloxacin Xanthan (0.3% ciprofloxacin in 0.6% xanthan). Each formulation was administered as a single topical drop (40 µl) at the time specified prior to infection. Five hours after infection, the corneas were harvested, homogenized and cultured to determine the log CFU per cornea ( SEM). Results: Administration of moxifloxacin or CILOXAN at 1, 3 or 5 hours prior to infection caused a significant decrease in the CFU per cornea relative to the untreated controls (P ≤ 0.0130). Moxifloxacin, but not CILOXAN, completely protected all corneas when applied at 1 or 3 hours prior to infection. Enhanced protectiveness of ciprofloxacin as a prophylactic medication was achieved using formulations with increased viscosity. The ciprofloxacin formulations containing either HPMC or xanthan gum had greater effectiveness than CILOXAN (P ≤ 0.0001). Ciprofloxacin Xanthan reduced the recoverable CFU in the cornea by more than 2 logs relative to the untreated control when administered at 5 hours prior to infection (P ≤ 0.0001). The ciprofloxacin HPMC formulation when administered at 5 or 8 hours prior to infection caused a 4 or 3 log reduction in CFU per cornea, respectively, relative to the untreated control (P ≤ 0.0001). Conclusion: Moxifloxacin demonstrated greater effectiveness for much longer period of time than CILOXAN in this prophylactic model. The effectiveness of ciprofloxacin as a prophylactic agent was enhanced by use of viscosity enhancing agents in the formulation.
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