Abstract
Purpose: :
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.
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Keywords: antibiotics/antifungals/antiparasitics