Antimicrobial performance of preservative agents in antiglaucoma ophthalmic solutions

Abstract

Purpose: We examined the antimicrobial performance of preservatives—benzalkonium chloride (BAC) at three different concentrations and the SofZia system—present in topical ocular hypotensive agents.

Methods: Four antiglaucoma ophthalmic solutions distributed in Japan—latanoprost (0.005%) with 0.02% BAC (Xalatan), bimatoprost (0.03%) with 0.005% BAC (LUMIGAN), tafluprost (0.0015%) with 0.001% BAC (TAPROS), and travoprost (0.004%) with SofZia (TRAVATANZ)—were tested for their antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Propionibacterium acnes, Streptococcus pneumoniae, and Candida albicans. Each drug solution (10 mL) was inoculated with 1 × 10⁶ colony-forming units of each organism and incubated at 20° to 25°C. Samples of each mixture collected at various times from 6 h to 28 days were serially diluted in Mueller-Hinton broth (for S. aureus, P. aeruginosa, E. coli and C. albicans), BL liquid medium (for S. pneumonia) or GAM liquid medium (for P. acnes) and plated in triplicate on tryptic soy agar (for S. aureus, P. aeruginosa, E. coli), BL agar plus horse blood (for S. pneumonia), GAM agar (for P. acnes) or Sabouraud dextrose agar (for C. albicans). Culture plates were incubated at 30° to 35°C for >3 days or at 20° to 25°C for >5 days, respectively, and the number of colonies was then counted.

Results: Latanoprost with 0.02% BAC completely inhibited bacterial growth after incubation for 24 h as well as fungal growth at 6 h. Bimatoprost with 0.005% BAC completely inhibited bacterial and fungal growth after incubation for 6 h. Tafluprost with 0.001% BAC completely inhibited bacterial growth after incubation for 7 days as well as fungal growth after incubation for 14 days. Travoprost with SofZia completely inhibited bacterial growth at 6 h but had no effect on fungal growth.

Conclusions: All four ophthalmic solutions performed well in tests of their antimicrobial activity. Only travoprost with the SofZia preservative system did not inhibit the growth of C. albicans within 28 days.