title: Rate of bacterial eradication by ophthalmic solutions of fourth-generation fluoroquinolones.
abstract: BACKGROUND
  Antibacterial activity of ophthalmic fourth-generation fluoroquinolones has traditionally been evaluated by comparing only their active ingredients, gatifloxacin and moxifloxacin. However, ophthalmic formulations of fourth-generation fluoroquinolones differ in terms of the inclusion of preservatives. While gatifloxacin ophthalmic solution 0.3% (Zymar; Allergan, Inc., Irvine, CA, USA) contains 0.005% benzalkonium chloride (BAK), moxifloxacin ophthalmic solution 0.5% (Vigamox; Alcon Laboratories, Inc., Fort Worth, TX, USA) is preservative-free. Recent studies have demonstrated that the presence of BAK dramatically affects the antibacterial activity of the ophthalmic formulation of gatifloxacin. This study was designed to compare the kill rates of ophthalmic solutions of fourth-generation fluoroquinolones against isolates of common ocular bacterial pathogens.
  
  
  METHODS
  Approximately 5.6 log(10) colony-forming units (CFU)/mL of Haemophilus influenzae (n=1), Streptococcus pneumoniae (n=1), Staphylococcus aureus (n=2), methicillin-resistant Staphylococcus aureus (MRSA) (n=4), methicillinresistant Staphylococcus epidermidis (MRSE) (n=4), and fluoroquinolone-resistant S. epidermidis (n=1) were incubated with ophthalmic solutions of either gatifloxacin or moxifloxacin. Viable bacteria were quantified at specific time points up to 60 minutes.
  
  
  RESULTS
  Gatifloxacin 0.3% completely eradicated H. influenzae and Strep. pneumoniae in 5 minutes, one of two S. aureus isolates in 15 minutes, and the other S. aureus isolate in 60 minutes. Gatifloxacin 0.3% completely killed all MRSA, MRSE, and fluoroquinolone-resistant S. epidermidis isolates in 15 minutes. Moxifloxacin 0.5% completely eradicated Strep. pneumoniae and one of four MRSA isolates in 60 minutes. All other isolates incubated with moxifloxacin 0.5% retained viable bacteria ranging from 1.8 to 4.4 log(10) CFU/mL.
  
  
  CONCLUSIONS
  The ophthalmic solution of gatifloxacin 0.3% eradicated bacteria that frequently cause postoperative ocular infections substantially faster than did the ophthalmic solution of moxifloxacin 0.5%.
authors.affiliation: Molecular Pathogenesis of Eye Infections Research Center, Dean A. McGee Eye Institute, Oklahoma City, Oklahoma, USA. michelle-callegan@ouhsc.edu
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Callegan
authors.forename: Billy D
authors.initials: BD
authors.lastname: Novosad
authors.forename: Raniyah T
authors.initials: RT
authors.lastname: Ramadan
authors.forename: Brandt
authors.initials: B
authors.lastname: Wiskur
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Moyer
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000627:therapeutic use*; D001372:Aza Compounds / Q000737:chemistry / Q000627:therapeutic use*; D001548:Benzalkonium Compounds / Q000627:therapeutic use; D015169:Colony Count, Microbial; D004353:Drug Evaluation, Preclinical; D024881:Drug Resistance, Bacterial; D009877:Endophthalmitis / Q000382:microbiology; D015818:Eye Infections, Bacterial / Q000382:microbiology* / Q000517:prevention & control; D024841:Fluoroquinolones / Q000737:chemistry / Q000627:therapeutic use*; D000077734:Gatifloxacin; D006193:Haemophilus influenzae / Q000187:drug effects; D006801:Humans; D007634:Keratitis / Q000382:microbiology; D000077266:Moxifloxacin; D009883:Ophthalmic Solutions / Q000737:chemistry / Q000627:therapeutic use*; D011183:Postoperative Complications / Q000382:microbiology; D011310:Preservatives, Pharmaceutical / Q000627:therapeutic use; D011804:Quinolines / Q000737:chemistry / Q000627:therapeutic use*; D013211:Staphylococcus aureus / Q000187:drug effects; D013212:Staphylococcus epidermidis / Q000187:drug effects; D013296:Streptococcus pneumoniae / Q000187:drug effects; D013997:Time Factors
chemical_list: D000890:Anti-Infective Agents; D001372:Aza Compounds; D001548:Benzalkonium Compounds; D024841:Fluoroquinolones; D009883:Ophthalmic Solutions; D011310:Preservatives, Pharmaceutical; D011804:Quinolines; D000077734:Gatifloxacin; D000077266:Moxifloxacin