Abstract
Abstract: :
Purpose: Preservatives are widely used in ophthalmic preparation to reduce microbial contamination and have been known to inhibit gram positive bacteria. Thus the antibiotics eye drops with preservative may act as a combination agent, while preservative free antibiotics act as a single agent. This study was to compare the in vitro antimicrobial efficacy of the new commercial formulations of fourth generation fluoroquinolone eye drops with and without preservatives against Staphylococcus species. Methods: Various strains of Staphylococcus from ATCC and ocular isolates were inoculated to the saline (inoculum control), moxifloxacin 0.5% (preservative free), and gatifloxacin 0.3% (preserved with BAK 0.005%). Inoculum control was serially diluted and incubated for the quantification. Serially diluted test samples were neutralized for 10 minutes and transferred to 0.45 µm polyethersulfone membrane filter units. The filters were plated to TSA plates and incubated for 72 hours at 35°C. Test samples were assayed at 15, 30, and 60 minutes. The antimicrobial efficacy was determined by quantitative bacteriologic analysis comparing logarithmic reduction of inoculum (CFU/ml). Results: The mean number of the measured inoculums were 4.8 x 105 CFU/ml. Logarithmic reductions of inoculum was 1.21 ± 0.64 at 15 minutes, 1.83 ± 0.91 at 30 minutes, and 2.78 ± 1.12 at 60 minutes with moxifloxacin, and 4.17 ± 1.05 at 15 minutes, 4.59 ± 0.21 at 30 minutes, and 4.62 ± 0.25 at 60 minutes with gatifloxacin. Conclusions: Gatifloxacin 0.3% exerted better in vitro antimicrobial efficacy than moxifloxacin 0.5% against Staphylococcus strains even at the lower concentration. Further studies addressing the synergistic antimicrobial contribution of the preservative agent (BAK 0.005%) with gatifloxacin and moxifloaxcin at similar concentrations seem warranted.
Keywords: antibiotics/antifungals/antiparasitics • Staphylococcus • bacterial disease