Purpose: To assess Pseudomonas aeruginosa growth in Refresh Plus(®), a unit-dose preservative-free ophthalmic solution indicated for the treatment of dry eye and after laser-assisted in situ keratomileusis (LASIK) surgery, which contains carboxymethylcellulose 0.5% as its active ingredient.
Methods: Multiple test tubes of Refresh Plus were inoculated with 3 clinical ocular isolates of P. aeruginosa to achieve a target concentration of ∼100 colony-forming units (CFU)/mL. The tubes were incubated at 25°C and samples were aseptically removed at 6, 12, and 24 h. The samples were cultured to enumerate the population at each time point.
Results: After 6 h incubation, the number of CFU/mL was 3,200 for isolate 1, 2,000 for isolate 2, and 6,480 CFU/mL for isolate 3. For all 3 organisms tested, the number of CFU/mL after 12 and 24 h incubation was >10(6) CFU/mL.
Conclusions: Under the conditions of this experiment, Refresh Plus appears to support P. aeruginosa growth, suggesting that if the solution in a unit-dose vial of Refresh Plus were contaminated with P. aeruginosa during use, the organism would survive and replicate in the solution over time. Noncompliance with the manufacturer's recommendations (i.e., reuse of an open vial) may result in contamination of the solution with P. aeruginosa, which may cause severe keratitis.