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E.C. Kim, P. Charukamnoetkanok, A.M. Poothullil, B. Paton, R.I. Pineda; Second, Third, and Fourth Generation Fluoroquinolone Susceptibilities of Methacillin Resistant Staph Aureus (MRSA) Cultures Collected at the Massachusetts Eye and Ear Infirmary . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2770.
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The use of topical fluoroquinilones for the treatment of ophthalmologic bacterial infections such as keratitis and for post–surgical infection prophylaxis is conventional in the U.S. We compared the susceptibility of fourth generation fluoroquinolones (FQs) (gatifloxacin (GAT) and moxifloxacin (MOX)), to third generation FQs (levofloxacin (LEV)), and to second generation FQs (ciprofloxacin (CIP) and ofloxacin (OFL)) by determining the minimum inhibitory concentrations (MICs in ug/ml) of staphylococcous species (staph spp.) patient cultures, including methicillin–resistant staphylococcus aureus (MRSA).
The MICs, the lowest concentration of drug that prevents visible growth of the organism, of staph spp. isolates were determined to MOX, GAT, LEV, CIP, and OFL using Etest, a quantitative technique for determining antimicrobial susceptibility using an antibiotic gradient along a strip placed on agar media plated with microorganisms.
Twenty–two staph spp. cultures were obtained from the ophthalmology and otolaryngology clinics at the Massachusetts Eye and Ear Infirmary over 6 months. Eleven of 22 were indentified as MRSA, and fluoroquinolone susceptibilities are listed below in Table I.
Our in vitro study suggests that the 4th generation FQs are more potent than the 2nd and 3rd generation FQs for MRSA. Additionally, within the 4th generation FQs, MOX is more potent than GAT for all staph spp. though potency is equal for MOX and GAT for MRSA. In vivo studies will be necessary to correlate this in vitro study.
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