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Published on: June 5, 2012
Pseudomonas aeruginosa growth in Refresh Plus®
Antonio Pinna1, Donatella Usai, Stefania Zanetti
1Section of Ophthalmology, Department of Surgery, Microsurgery, and Medico-surgical Specialties, University of Sassari, Sassari, Italy. apinna@uniss.it
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.
Insights
Pseudomonas aeruginosa can grow in Refresh Plus, a preservative-free eye drop. Contaminated eye drops, especially if reused, may lead to severe keratitis.
Area of Science:
- Ophthalmology
- Microbiology
- Pharmaceutical Science
Background:
- Dry eye and post-LASIK surgery patients often use preservative-free ophthalmic solutions.
- Unit-dose eye drops are intended for single use to maintain sterility.
Purpose of the Study:
- To evaluate the growth potential of Pseudomonas aeruginosa in Refresh Plus, a unit-dose preservative-free ophthalmic solution.
- To understand the implications of potential contamination in ophthalmic solutions used for dry eye and post-LASIK care.
Main Methods:
- Inoculation of Refresh Plus with three clinical isolates of P. aeruginosa.
- Incubation at 25°C with sampling at 6, 12, and 24 hours.
- Culturing to determine bacterial population (CFU/mL) at each time point.
Main Results:
- P. aeruginosa demonstrated significant growth in Refresh Plus.
- Bacterial counts increased from approximately 100 CFU/mL to over 10^6 CFU/mL within 24 hours.
- All tested isolates showed robust replication in the ophthalmic solution.
Conclusions:
- Refresh Plus supports the growth of P. aeruginosa under experimental conditions.
- Contamination of unit-dose vials, particularly through reuse, poses a risk of bacterial proliferation.
- Potential for severe keratitis exists if contaminated solutions are used, highlighting the importance of proper usage.
