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W. Haas, L. S. Brunner, C. Pillar, T. W. Morris; Bactericidal Activity of Besifloxacin and Other Ophthalmic Antibacterials Against Recent Ocular Isolates. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2675.
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Besifloxacin is a novel fluoroquinolone developed for the topical treatment of ophthalmic infections. Fluoroquinolones are widely used antibacterials with potent bactericidal activity, which can confer significant advantages in the treatment of infections in immune-privileged sites, such as the eye. This study examined the bactericidal activity of besifloxacin and relevant comparators against the most common causes of bacterial conjunctivitis.
Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined for 120 recent ocular isolates of the four most common causes of bacterial conjunctivitis. Isolates were tested in accordance with CLSI standards. The MBC was defined as the drug concentration that resulted in a 99.9% decrease in viable cell counts. Antimicrobials in the MBC study included besifloxacin, ciprofloxacin, gatifloxacin, moxifloxacin, azithromycin, and tobramycin. Time kill experiments were performed for selected ocular isolates, including drug resistant strains, in the presence of besifloxacin, moxifloxacin and ciprofloxacin.
The fluoroquinolones and tobramycin showed bactericidal activity for all species tested, while azithromycin was generally bactericidal for Streptococcus pneumoniae and Haemophilus influenzae, and generally bacteriostatic for Staphylococcus aureus and Staphylococcus epidermidis. Besifloxacin was bactericidal against all 120 isolates tested, including ciprofloxacin-resistant MRSA and MRSE isolates, penicillin resistant S. pneumoniae, and beta-lactamase positive H. influenzae. Time kill curves confirmed that besifloxacin showed concentration dependent bactericidal activity against quinolone susceptible and resistant isolates.
Besifloxacin was bactericidal for all bacterial species tested (S. aureus, S. epidermidis, S. pneumoniae and H. influenzae), including drug resistant strains. In addition, besifloxacin had the lowest MICs and MBCs of all tested agents.
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