RESUMEN
Purpose: To compare equal concentrations (0.5%) of moxifloxacin and gatifloxacin ophthalmic solutions with regard to conjunctival bacterial reduction as well as anterior chamber penetration. Methods: One hundred patients were divided into 2 groups. Group A received moxifloxacin 0.5% ophthalmic solution and group B received gatifloxacin 0.5% ophthalmic solution 4 times a day for 3 days before surgery and 5 times with 30 min intervals on the day of surgery. Two conjunctival swabs were obtained: one before instillation of antibiotic and the second 30 min after instillation of the last antibiotic drop. Specimens were sent for culture and susceptibility testing. At the time of surgery, 0.1 mL of aqueous fluid was aspired, and aqueous concentration of fluoroquinolones was identified using reverse-phase high-pressure liquid chromatography assay technique. Results: The most common flora isolated was coagulase-negative Staphylococcus (32.9%), followed by Staphylococcus aureus (24.8%) and Corynebacterium diphtheria (19.1%). Moxifloxacin aqueous concentration was higher compared with gatifloxacin [1.75 ± 0.98 standard deviation (SD) and 0.75 ± 0.22 SD, respectively]. This 2.3-fold difference in aqueous humor antibiotic concentrations was statistically significant (P ≤ 0.001). There was significant difference between the means of conjunctival colony-forming unit after antibiotic administration in both the study groups (2.17 ± 1.54 SD in group A and 1.56 ± 1.09 SD in group B). Conclusions: Moxifloxacin 0.5% was found to penetrate anterior chamber more than gatifloxacin 0.5%, enforcing its use for prophylaxis before intraocular surgeries. However, gatifloxacin 0.5% eye drops were able to reduce conjunctival bacterial load, more supporting its use before extraocular and refractive surgeries.