The Minimum Concentration and Preservation Time of Ethanol for Sterilization of Donor Sclera: In Vitro Study

ABSTRACT

PURPOSE: We studied to investigate the minimum concentration and preservation time of ethanol for sterilization of donor sclera. METHODS: Fresh sclera was inoculated with Staphylococcus epidermidis(ATCC 155), Staphylococcus aureus(ATCC 28213), Pseudomonas aeruginosa(ATCC 27843), and transferred to preservative vials containing the concentration of ethanol(10, 30, 50, 70, and 90%) or trypticase soy broth(TSB, control) and stored at room temperature. The sclera was then homogenized, plated on blood agar, and incubated at 37 degreesC for 24 hours. Colonies were counted at 6, 12, 24, 48, and 72 hours. RESULTS: Staphylococcus epidermidis and Staphylococcus aureus were recovered from contaminated sclera plates preserved in 10% ethanol until 72 hours and in 30% ethanol until 12 hours, but no bacteria was recovered from the sclera preserved in more than 50% ethanol(P<0.05). Pseudomonas aeruginosa was recovered in 10% ethanol until 72 hours but not recovered in more than 30% ethanol until 24 hours(P<0.05). However, all three species were recovered from the control sclera preserved in TSB until 72 hours. CONCLUSIONS: From the above results it is concluded that the concentration of more than 50% ethanol for at least 6 hours is recommendable as human sclera disinfectants.