Eyebank Prep Processes Promote Fungal Growth in Endothelial Keratoplasty Tissue

By Lorraine L. Janeczko

October 11, 2017

NEW YORK (Reuters Health) – Fungi are more likely to grow when donor corneal tissue is processed for endothelial keratoplasty than for other uses, perhaps because of the greater time spent at room temperature, according to data from the Eversight Eyebank Study.

"Tissues exposed to less time at room temperature (penetrating keratoplasty and anterior lamellar keratoplasty tissue) had less detectable Candida at the time of transplant than tissues that were exposed to more time at room temperature," principal investigator Dr. Elmer Y. Tu of the University of Illinois in Chicago told Reuters Health by email.

"Although the risk remains small, the finding not only confirms that there is an increased risk of fungal - specifically Candida - infection in patients receiving endothelial corneal transplants, but that the risk may stem from fungal proliferation during the extended amount of time at room temperature exposure inherent to the tissue processing needed to prepare the grafts," he said.

As reported online September 28 in JAMA Ophthalmology, Dr. Tu and his colleagues examined the 2013 Eversight Eyebank Study follow-up database of 6,592 corneal transplants for risk factors associated with post-keratoplasty infection.

They also assessed fungal colony-forming units from optisol-gentamicin and streptomycin (OptiSol-GS) storage media inoculated with Candida albicans, Candida glabrata, and Candida parapsilosis endophthalmitis isolates. Two incubation temperatures were used to mimic different pre-surgical corneal tissue processing protocols.

Donor rim cultures were about three times more likely to be positive for fungi in tissue processed for endothelial keratoplasty than for other uses (1.14% vs. 0.37%; P=0.009).

In vitro, more time spent at room-temperature incubation of OptiSol-GS increased the growth of Candida species. Adding caspofungin and voriconazole reduced Candida growth.

"It is vitally important to understand that the contamination is not likely introduced in the eyebank but is a result of increased growth of Candida that is already present in the donor tissue,” Dr. Tu explained.

"Endothelial keratoplasty has been an incredible advance in the treatment of certain corneal diseases and very quickly has become the most common type of corneal transplant performed in the United States,” he noted. “For all patients who need to be maintained on immunosuppressive topical corticosteroid drops, fungal infections of any corneal transplant can be devastating, but especially in endothelial keratoplasty patients where they could need another transplant or, in rare cases, lose the eye. The main question that remains is the optimal concentration and choice of antifungal supplementation to use for optimal efficacy and toxicity."

Lead study author Dr. Kimberly M. Brothers, of the University of Pittsburgh, told Reuters Health by email, "Donor tissues are often contaminated with fungi. We demonstrated how quickly the fungi can grow when exposed to multiple room-temperature incubations and also how effective the antifungals tested can be at reducing or eliminating growth of certain Candida species. Since one antifungal alone was not sufficient to reduce or eliminate growth of multiple Candida species, supplementing OptiSol-GS corneal storage media with a mixture of antifungals may be more effective and prevent fungal infection in patients who receive contaminated donor tissue."

Dr. Anthony J. Aldave of the Jules Stein Eye Institute in Los Angeles, and chair of the Eye Bank Association of America Medical Advisory Board Subcommittee on Fungal Infection After Corneal Transplantation, said in an email, "As endothelial keratoplasty is the most common form of corneal transplantation performed in the United States, it is important to determine why it is associated with an increased risk of transmission of fungal infection to the recipient and what can be done to decrease” that risk.

"Modification of donor cornea processing procedures in the eyebank, including the possible addition of antifungal medications to the donor cornea storage solution, may decrease the risk of fungal infection in donor cornea recipients," he advised.

Dr. Julie Schallhorn of the University of California, San Francisco, told Reuters Health by email, "The results of this study add to a growing body of knowledge that supports the consideration of adding antifungal agents to OptiSol-GS. This study also suggests an additional way of addressing the increasing prevalance of positive fungal cultures: by revising the preparation procedures for corneal grafts and perhaps by maintaining them in cold storage during eyebank preparation."

Dr. Aldave and Dr. Schallhorn were not involved in the study.

SOURCE: http://bit.ly/2y9Hk9z

JAMA Ophthalmol 2017.