title: Kill rates of preserved and preservative-free topical 8-methoxy fluoroquinolones against various strains of Staphylococcus.
abstract: OBJECTIVE
  To assess the kill rates of preserved and preservative-free 8-methoxy fluoroquinolones and benzalkonium chloride (BAC) against isolates of Staphylococcus aureus and coagulase-negative Staphylococcus (CNS) species.
  
  
  METHODS
  Bascom Palmer Eye Institute, Miami, Florida, USA.
  
  
  METHODS
  Ocular and standard isolates of S aureus and CNS were inoculated with saline, 0.005% BAC, gatifloxacin 0.3% containing 0.005% BAC (Zymar), or BAC-free moxifloxacin 0.5% (Vigamox) at 37 degrees C. Bacterial viability was assessed after 15 minutes, 30 minutes, and 60 minutes.
  
  
  RESULTS
  Thirteen isolates of S. aureus and 5 isolates of CNS were used. The mean initial load of bacterial inoculum was 5.45 log colony-forming units (CFU)/mL +/- 0.37 (SD). Saline did not affect the density of staphylococci; BAC significantly decreased the staphylococci count to a mean of 3.80 +/- 0.32 log CFU/mL at 60 minutes (P<.05). Gatifloxacin 0.3% reduced the number of staphylococci significantly more than moxifloxacin 0.5% at 15 minutes (mean 0.47 +/- 1.12 log CFU/mL versus 4.55 +/- 0.60 log CFU/mL), 30 minutes (mean 0.07 +/- 0.31 log CFU/mL versus 3.82 +/- 1.07 log CFU/mL), and 60 minutes (mean 0.00 +/- 0.00 log CFU/mL versus 2.75 +/- 1.29 log CFU/mL) (P<.005). Gatifloxacin 0.3% completely eradicated most S. aureus (10/13) and CNS (3/5) isolates at 15 minutes; moxifloxacin 0.5% did not achieve complete kill in any S. aureus isolate (13/13) or in most CNS isolates (4/5) at 60 minutes.
  
  
  CONCLUSIONS
  The commercial formulation of gatifloxacin 0.3% containing BAC 0.005% completely eradicated staphylococcal isolates more rapidly than the BAC-free formulation of moxifloxacin 0.5% or BAC 0.005% alone.
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Joon Young
authors.initials: JY
authors.lastname: Hyon
authors.forename: Ilker
authors.initials: I
authors.lastname: Eser
authors.forename: Terrence P
authors.initials: TP
authors.lastname: O'Brien
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D015169:Colony Count, Microbial; D024841:Fluoroquinolones / Q000494:pharmacology*; D000077734:Gatifloxacin; D006801:Humans; D008826:Microbial Sensitivity Tests; D011310:Preservatives, Pharmaceutical / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000890:Anti-Infective Agents; D001548:Benzalkonium Compounds; D024841:Fluoroquinolones; D011310:Preservatives, Pharmaceutical; D000077734:Gatifloxacin