Antimicrobial In Vitro Evaluation of Corneal Storage Media using a Closed Chamber Study Model 

Purpose: To evaluate in vitro the antimicrobial influence of the corneal storage media containing antibiotics using a closed chamber study model under the closest simulated environment of corneal preservation process. Materials and Methods: Samples of cornea storage media containing streptomycin and gentamicin (Optisol-GS®) were analyzed at different moments after its contamination with Staphylococcus aureus (ATCC25923). Samples were analyzed at 1, 2, 3, 4, 5, 6, 24, 48, 72 hours; 7 days; and 14 days after contamination. The samples were analyzed using a new study model system that consists of two closed coupled chambers. The upper chamber contained two culture media (chocolate agar and Sabouraud agar) and CO₂ indicator (indication of bacterial aerobic activity). The inferior chamber contained supplemented solution with an antimicrobial inhibitor. The bacterial growth parameters were analyzed by the presence or absence of bacteria in chocolate agar and by color change of CO₂ indicator when positive. First reading was performed after 24 hours, and, in the absence of bacterial growth, a second reading was carried out after 48 hours. Results: Color change in CO₂ indicator was found in samples contaminated after 1, 2, and 3 hours on the first reading. On the second reading, we observed color change in all remaining samples, except for samples contaminated after 14 days. Conclusion: Samples of cornea storage media containing gentamicin sulphate and streptomycin sulphate in vitro showed viable Staphylococcus aureus for up to 7 days of contamination.