J Korean Ophthalmol Soc.  2020 May;61(5):466-471. 10.3341/jkos.2020.61.5.466.

Serial Culture of Eyedrops: Room Temperature vs. under Refrigeration

  • 1Kim’s Eye Hospital, Seoul, Korea


We investigated the serial culture of multiuse eye drops applied by medical personnel by intentionally touching the tip of the bottle.
Ten different unpreserved and preserved eye drops including eye drops for allergies, artificial tears, antibiotics, and corticosteroids were included. One bottle was stored at room temperature and the other bottle stored under refrigeration. The experimenter intentionally touched the tip of the bottle with a finger twice daily. The first culture test was performed 2 weeks after contamination and the culture were performed six times; 2 weeks apart.
Contamination was noted in three types of eye drops (artificial tears without preservatives, corticosteroids, and anti-allergic eye drops) under refrigerated conditions and four types of eye drops (artificial tears without preservatives, artificial tears with preservatives, corticosteroids, and anti-allergic eye drops) under room temperature conditions. The contamination in 13 eye drops was attributable to five microbial species: Staphylococcus epidermidis (m/c), Staphylococcus hominis, Rhodotorula sp., Corynebacterium sp., and Bacillus sp. Under refrigerated conditions, three eyedrop bottles were contaminated, with five positive cultures in 12 weeks. However, at room temperature, four eye drop bottles were contaminated with eight positive cultures. The culture results changed according to culture time. In some cases, the same result was obtained 2 weeks after the first positive culture but in other cases the result was negative or one of two strains disappeared.
Eye drops can be contaminated under both room temperature and refrigerated conditions. We should consider serial culture for eye drops because the culture results could be variable according to time.


Culture; Drug contamination; Ophthalmic solutions
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