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J. M. Blondeau, S. D. Borsos, C. Hesje; Rate of Methicillin-Resistant Staphylococcus aureus (MRSA) Eradication by Fourth-Generation Fluoroquinolones at Physiologically Relevant Concentrations. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5944.
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Zymar contains 3000 µg/mL of gatifloxacin (GAT) and is preserved with 0.005% (50 µg/mL) benzalkonium chloride (BAK) whereas Vigamox contains 5000 µg/mL of moxifloxacin and is preservative free. This study was designed to determine the rate of MRSA eradication by fourth-generation fluoroquinolones at physiologically relevant concentrations.
Four clinical MRSA isolates were grown in Mueller-Hinton broth. Bacteria (105 colony forming units/mL) were then incubated with gatifloxacin in the presence and absence of BAK, Zymar, or Vigamox under ambient conditions. The log10 reduction and percentage of killed bacteria were determined after 5, 25, and 120 minutes.
GAT at concentrations of 300 µg/mL and 600 µg/mL killed 39% to 99% of bacteria in 5 to 120 minutes (Table). GAT (300 µg/mL) plus BAK (15 µg/mL) eradicated 70% to 99% of MRSA over the same time period. Zymar at GAT equivalent concentration of 300 µg/mL eradicated 70% to 99% of MRSA whereas Vigamox at moxifloxacin equivalent concentration of 500 µg/mL killed 32% to 52% of bacteria in 5 to 120 minutes (Table).
GAT at physiologically relevant concentrations rapidly eradicated MRSA isolates. BAK enhanced bactericidal activity of GAT. Zymar was as effective as GAT plus BAK and superior to Vigamox in eradicating MRSA isolates.
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