False negative results in microbiological analyses of corneal tissues EATB

Abstract: The use of antibiotic cocktails during corneal processing can lead to an antibiotic carry-over effect, which in turn can generate false negative results in microbiological analysis.
The aim of the study was to investigate the impact of antibiotic residues on microbiological analyses of organ cultured donor corneas.
Sixty-one corneal tissues unsuitable for transplantation were retrieved by the personnel of two Italian eye banks and transported to the bank in Eusol-C (AL.CHI.MI.A. Srl, Italy); After transfer to Tissue-C (AL.CHI.MI.A. Srl, Italy), corneas were stored for 12-14 days at 31°C.
Microbiological analyses were performed post-processing on Tissue-C by the eye banks, according to bank standard procedures using BACTEC plus aerobic/anaerobic system (BD); in parallel, microbiological analyses were performed by AL.CHI.MI.A. Srl with sterility test according to the European Pharmacopeia, after removing potential interfering antibiotics with RESEP (AL.CHI.MI.A. Srl, Italy).
Sterility test after removing potential interfering antibiotics with RESEP showed an average of 59% positive samples at the end of the process; the percentage of positive results varied depending on the Bank. None of these contaminations was detected by BACTEC.
Removal of antibiotic residues from corneal storage media with the RESEP device resulted in a significant number of false negative results in the microbiological analyses.
The presence of contaminants in the media at the end of the storage process indicates that standard corneal storage media does not warrant efficient corneal decontamination.