Detection of endotoxin in media from sterile corneal organ cultures

Lipopolysaccharides (LPS) are elements of the cell wall of gram-negative bacteria. They are also called endotoxins and are known to stimulate various inflammatory reactions by interaction with cytokines and macrophages. Additionally, they may have a direct effect on other cells. As contamination of sterile organ-culture media with bacterial substances may influence the donor-tissue prognosis, we investigated a series of culture media drawn from organ culture for the presence of endotoxin. A total of 341 samples of sterile organ-culture media from 3 different cornea banks using either organ culture or the refrigerated-storage technique were tested for endotoxin. The assay was performed using the Limulus amebocyte-lysate test. A level of endotoxin above the background threshold was found in 99/341 (29%) culture media. The incidence of endotoxin ranged from 14% up to 50%, depending on the cornea bank and culture system used. Endotoxin detected in sterile corneal organ cultures probably derives from nonreplicating bacterial postmortem donor-tissue contamination. The presence of endotoxin-positive cultures varied between the eye banks but was not related to a given storage method. As endotoxin may directly influence graft viability or trigger inflammatory host responses, these findings may have significance for the clinical results of corneal grafting.