Microbial Contamination in Corneas Stored in Organ Culture Media: A 30 Month Report from the Lions New South Wales Eye Bank

Abstract

Purpose : Microbial contamination is one of the major factors causing corneal tissue loss in Eye Banking. The purposes of this study were to assess corneal tissue in organ culture that resulted in positive microbiology and to analyse the major factors that may relate to the contamination.

Methods : Data from the Lions New South Wales Eye Bank (LNSWEB) between the 1^st of September 2011 and the 30^th of April 2014 prior to the introduction of eye bank corneal pre-preparation protocol were reviewed retrospectively. All corneas were stored in organ culture storage media (OCS) using standard protocol. Eyes were decontaminated with 5% povidone iodine for 5 minutes. At day 3, 3 ml of OCS was inoculated in a pair of Bactec Plus Aerobic/F and Bactec Lytic/10 Anaerobic/F culture bottles and placed in a Bactec 9240 incubator for 5 days at 37°C. This test was repeated 1 day after the tissue was transferred into organ culture transport medium (OCT). The corneas were divided into positive and negative groups according to both OCS and OCT culture results. For each demographic factor including age, gender, time from death to enucleation, time to preservation and tissue collecting season was analysed between the two groups. An odds ratio and an overall p value considering all possible comparisons of each subgroup was generated for each factor.

Results : A total of 1708 corneas were included in the analysis with a total of 47 cases of microbial contamination, representing a contamination rate of 2.75%. Female showed higher contamination rate than male donors (odds ratio=2.28; p=0.0111). The main contaminants were Candida species followed with Coagulase Negative Staphylococcus. Tissues collected in summer and autumn had high contamination rate (odds ratio=1.56 and 1.84 respectively, p=0.03). Rates of contamination varied from 0 to 12.5% for all institutions with a trend to high contamination rates from remote institutions. Age, time from death to enucleation and time to preservation had no correlation with microbial contamination.

Conclusions : A contamination rate of 2.75% is in the low range compared to reported data from other Eye Banks and represents the laboratory protocols and donor selection criteria utilised by the dedicated staff at the LNSWEB. With Candida species contributing the largest percentage of contamination, specific measures to combat fungal contamination should be considered.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.