Dual-system microbiological screening to prevent fungal transmission in corneal grafts: a four-year eye bank retrospective study

<title>Abstract</title> <p> Background This study aimed to assess the effectiveness of a dual-system microbiological screening protocol implemented at the Emilia-Romagna Eye Bank in preventing fungal (specifically <italic>Candida</italic> ) transmission in corneal grafts. Secondary objectives included identifying donor- and medical history-related risk factors for corneal contamination and strategies for managing "mate corneas" (paired corneas from a donor with one contaminated cornea). Methods A retrospective analysis was conducted of 2,273 corneal transplants performed and 3,138 donor corneas processed between January 2020 and December 2023. The dual-system screening used organ culture preservation, combined with turbidimetric and fluorimetric microbiological tests. Results Under the new protocol, no cases of postoperative Candida-related keratitis or endophthalmitis were observed among 2,255 transplanted corneas, representing a significant improvement over the previous 5 Candida-related complications in 5 transplants. Of the 3,138 donor donations analysed, 204 (6.5%) showed bacterial or fungal contamination, with 136 (4.3%) specifically positive for <italic>Candida</italic> . Significant risk factors for contamination included younger donor age, donation during the summer months, neoplastic disease, and longer death-to-explant intervals. The majority (62.3%) of mate corneas from donors with one contaminated cornea were discarded due to confirmed contamination or altered morphology. Conclusions The implemented dual-system microbiological screening protocol proved highly effective in preventing postoperative fungal infections among corneal transplant recipients. Donor age, seasonality, and post-mortem interval were identified as primary risk factors for corneal contamination. The findings support the wider adoption of comprehensive microbiological screening and organ culture techniques to improve transplant safety and optimise graft utilization. </p>