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C.M. Nedrud, R.W. Snyder, D.E. Nix, J. Lee, M. Chang; Comparing Kill Rates for Two New Fluoroquinolones to Ofloxacin and Vancomycin Against Staphylococcal Endophthalmitis Isolates . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2120.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The effectiveness of intracameral antibiotics for prophylaxis against endophthalmitis following cataract surgery maybe limited due to the dilution effect from the quick turn over of aqueous humor (t1/2 ~ 2 hrs.) and either slow killing or low potency. The enhanced gram-positive potency and concentration-dependent killing of newer fluoroquinolones may result in rapid killing. To help test this hypothesis, we compared the kill rates of gatifloxacin and moxifloxacin to ofloxacin and vancomycin against Staphylococcus aureus (SA) and coagulase-negative Staphylococcus (CNS) endophthalmitis isolates. Methods: Fifteen Staphylococcus isolates (9 SA and 6 CNS) were collected from endophthalmitis cases. One of the CNS isolates was excluded from the study due to slow growth of the control. Bacterial killing was assessed by examining the average log change (compared to baseline) of the isolates versus different drug concentrations after 4 hours of drug exposure. Each drug was tested at set concentrations (4, 20, and 64 µ g/ml for gatifloxacin, 0.5, 4, and 16 µ g/ml for moxifloxacin, 20, 40, and 80 µ g/ml for ofloxacin, and 1, 4, and 16 µ g/ml for vancomycin). Results: Gatifloxacin and moxifloxacin both demonstrated an average of 3 logs of kill against the SA isolates at concentrations ≥ 4 µ g/ml. Vancomycin at 4 µ g/ml produced 1.21 logs of kill after 4 hours and had no increase in killing at higher concentrations. Maximum killing with ofloxacin was 2.15 to 2.08 logs at 40 and 80 µ g/ml, respectively. Against CNS, gatifloxacin and moxifloxacin had similar results to vancomycin at 4 µ g/ml (gatifloxacin 1.92 logs, moxifloxacin 1.73 logs, and vancomycin 1.88 logs of killing), but were more effective at higher concentrations (2.7 logs of kill at 20 µ g/ml of gatifloxacin and 2.5 logs of kill at 16 µ g/ml of moxifloxacin). Ofloxacin achieved only 1.14 logs of kill at its highest concentration (80 µ g/ml) against CNS. Conclusions: Gatifloxacin and moxifloxacin are both very effective at killing the Staphylococcal isolates. Due to their ability to rapidly kill bacteria, they maybe useful when given intracamerally to prevent endophthalmitis following cataract surgery.
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