Factors affecting corneal organ culture contamination: a 6-year study at the New South Wales Tissue Bank

Purpose: To report the rate of microbial contamination and analyze possible risk factors for contamination of banked corneas stored using the organ culture method. Methods: Data from the New South Wales Tissue Banks incorporating the Lions NSW Eye Bank, between September 1, 2011, and November 30, 2017, were reviewed retrospectively. All corneas collected during this period and stored in organ culture storage media were tested for microbial contamination. The influence of potential factors on the rate of contamination was analyzed using the χ² test and logistic regression using generalized estimating equations. Results: A total of 4410 corneas were included in this study, of which 110 were medium culture positive, representing a microbial contamination rate of 2.5%. The main contaminants were Candida species followed by Staphylococcus species. Corneal tissue collected in summer and autumn had a significantly higher contamination rate (P = 0.006). All other factors studied were not shown to have a statistically significant association with contamination after accounting for within-pair correlation and confounders. Conclusions: A relatively low contamination rate of 2.5% observed in our study reflects the stringent laboratory protocols, strict donor selection criteria, and high level of experience among staff at the Lions NSW Eye Bank. Our study demonstrated that the season of collection had a strong association with the rate of organ culture contamination. Because Candida species contributed the largest percentage of contamination, specific measures to reduce and eliminate fungal proliferation should be considered by eye banks particularly in warm seasons.