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S.D. Borsos, J.M. Blondeau; Antimicrobial Efficacy of Gatifloxacin With and Without Benzalkonium Chloride Compared With Moxifloxacin Against Common Ocular Pathogens . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1892.
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To evaluate the antimicrobial efficacy of gatifloxacin with and without benzalkonium chloride (BAK) compared with moxifloxacin against Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Pseudomonas aeruginosa.
MIC testing was by microbroth dilution in accordance with the recommended CLSI procedure. Approximately 105 CFU/mL of each organism was added to appropriate media containing two–fold concentration increments of drug. For experiments containing BAK, 2.5 µL of a 10% solution was added to the first well of the plate to give a final BAK concentration of .0125%, and then was serially diluted with the drug; subsequently diluted at 1:2 when adding organisms to each well. Plates were incubated for 18 hours in ambient air and the lowest concentration showing no growth was recorded as the MIC.
The MIC90 values of gatifloxacin plus BAK were lower than the MIC90 values of either fluoroquinolone alone for every tested organism. Against specific organisms, the MIC90 values were as follows: H. influenzae: 0.004 µg/mL with gatifloxacin/BAK, 0.031 µg/mL with gatifloxacin, and 0.031 µg/mL with moxifloxacin; S. pneumoniae: 0.001 µg/mL with gatifloxacin/BAK, 0.25 µg/mL with gatifloxacin, and 0.125 µg/mL with moxifloxacin; S. aureus: 0.004 µg/mL with gatifloxacin/BAK, 0.063 µg/mL with gatifloxacin, and 0.031 µg/mL with moxifloxacin; P. aeruginosa: 0.5 µg/ml with gatifloxacin/BAK, 4.0 µg/mL with gatifloxacin, and 8.0 µg/mL with moxifloxacin.
The combination of gatifloxacin and BAK was highly efficacious against a variety of common ocular pathogens in vitro, providing MIC90 values that were 8– to 125–fold lower than the moxifloxacin MIC90.
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