Purpose This retrospective study aims to compare the rate of microbial contamination in fresh, non-preserved amniotic tissue as opposed to decontaminated cryopreserved tissue, thereby being able to determine the efficiency of the decontamination procedures applied during amniotic tissue preparation in the Cornea Bank Essen.

Methods The amniotic tissue was retrieved from donor placentas acquired through elective c-section. Tissue preparation was performed according to standard operation procedures of the Cornea Bank Essen. Briefly, the tissue is rinsed with sterile balanced salt solution (BSS) and decontaminated with BSS containing anti-infectives. Preservation included the application of a cryopreservation solution containing anti-infectives and glycerin. The tissue is stored at a temperature of -80°C. Screening for microbial contamination of amniotic tissue in its pre- and post decontamination status is part of the process.

In this study, data from 107 placentas prepared in the eye bank were retrospectively evaluated for the microbiological status to determine the effectivity of the procedure.

Results Out of the fresh, non-preserved amniotic tissue, 53 were tested positive for microbial contamination. The most common species identified were C.acnes and Staphylococcus spp., which jointly comprised around 80% of the detected microorganisms. Others found in the remaining placentas were of the species: Acinetobacter, Bacillus spp., Faklamia, Lactobacillus, Rothia, Micrococcus, Penicillium, Ralstonia, Streptococcus and non-specific aerobic sporulating bacteria.

In contrast, 8 samples of the decontaminated cryopreserved tissue were tested positive for microorganisms with 4 placentas inhabited by C.acnes, 2 by Bacillus spp. while the remaining consisting each of the species Staphyloccocus and Ralstonia.

Conclusion Overall, the decontamination measures applied during the preparation of the amniotic tissue can be regarded as effective. We found a significant reduction of the number of microorganisms detected in the amniotic tissue following antibiotic administration.

However, some of the remaining species identified in the processed samples may be considered as contamination during the preparation and testing procedures.

For instance, C.acnes can be considered a result of secondary contamination due to incorrect handling. Species such as Bacillus most likely managed to endure the decontamination process owing to its natural resilience against harsh circumstances.