Zymar (Gatifloxacin 0.3%) shows excellent Gram-negative activity against Serratia marcescens and Pseudomonas aeruginosa in a New Zealand White rabbit keratitis model.

Abstract

PURPOSE:

Whereas gatifloxacin, a newer fluoroquinolone, was engineered to increase its Gram-positive potency, we assessed whether it still retained significant Gram-negative activity in vivo. Specifically, we compared the efficacy of Zymar (gatifloxacin 0.3%), Ciloxan (ciprofloxacin 0.3%), and fortified tobramycin (14 mg/mL) in the treatment of experimental Gram-negative bacterial infections of Serratia marcescens (SM) and Pseudomonas aeruginosa (PA) in the New Zealand White (NZW) rabbit keratitis model.

METHODS:

A total of 30 NZW rabbits each were intrastromally inoculated in both eyes with approximately 1000 CFU of SM and PA. By E-test, the minimum inhibitory concentrations (MICs; microg/mL) for SM were gatifloxacin (0.125), ciprofloxacin (0.047), and tobramycin (1.5), and for PA were gatifloxacin (0.125), ciprofloxacin (0.19), and tobramycin (0.5). After 16 hours, the rabbits were divided into 4 treatment groups: (1) Zymar, (2) Ciloxan, (3) fortified tobramycin, and (4) saline control. One drop was instilled in both eyes every 15 minutes for 5 doses and then every 30 minutes for 14 doses. One hour after the final treatment, the animals were euthanized, and bacterial colony counts from the corneas were determined.

RESULTS:

For SM, Zymar and Ciloxan significantly reduced (P < 0.001, ANOVA) the colony counts compared with tobramycin and saline control. Zymar was more effective than Ciloxan (P < 0.001, ANOVA). For PA, all antibiotics reduced equivalently the colony counts compared with the saline control (P = 0.005, ANOVA).

CONCLUSIONS:

The enhanced Gram-positive activity of gatifloxacin is not associated with any decreased Gram-negative activity in vivo. Zymar may prove useful for SM and PA keratitis.

• Authors: Francis S Mah, Eric G Romanowski, Regis P Kowalski, Kathleen A Yates, Y Jerold Gordon
• Journal: Cornea (Cornea) Vol. 26 Issue 5 Pg. 585-8 (Jun 2007) ISSN: 0277-3740 [Print] United States
• PMID: 17525656 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Infective Agents
• Fluoroquinolones
• Ciprofloxacin
• Gatifloxacin
• Tobramycin

Topics

• Animals
• Anti-Infective Agents (therapeutic use)
• Ciprofloxacin (therapeutic use)
• Colony Count, Microbial
• Corneal Ulcer (drug therapy, microbiology)
• Disease Models, Animal
• Eye Infections, Bacterial (drug therapy, microbiology)
• Female
• Fluoroquinolones (therapeutic use)
• Gatifloxacin
• Pseudomonas Infections (drug therapy, microbiology)
• Pseudomonas aeruginosa (drug effects, isolation & purification)
• Rabbits
• Serratia Infections (drug therapy, microbiology)
• Serratia marcescens (drug effects, isolation & purification)
• Tobramycin (therapeutic use)