Residual Antibiotics in Decontaminated Human Cardiovascular Tissues Intended for Transplantation and Risk of Falsely Negative Microbiological Analyses

Abstract

We investigated the presence of antibiotics in cryopreserved cardiovascular tissues and cryopreservation media, after tissue decontamination with antibiotic cocktails, and the impact of antibiotic residues on standard tissue bank microbiological analyses. Sixteen cardiovascular tissues were decontaminated with bank-prepared cocktails and cryopreserved by two different tissue banks according to their standard operating procedures. Before and after decontamination, samples underwent microbiological analysis by standard tissue bank methods. Cryopreserved samples were tested again with and without the removal of antibiotic residues using a RESEP tube, after thawing. Presence of antibiotics in tissue homogenates and processing liquids was determined by a modified agar diffusion test. All cryopreserved tissue homogenates and cryopreservation media induced important inhibition zones on both Staphylococcus aureus- and Pseudomonas aeruginosa-seeded plates, immediately after thawing and at the end of the sterility test. The RESEP tube treatment markedly reduced or totally eliminated the antimicrobial activity of tested tissues and media. Based on standard tissue bank analysis, 50% of tissues were found positive for bacteria and/or fungi, before decontamination and 2 out of 16 tested samples (13%) still contained microorganisms after decontamination. After thawing, none of the 16 cryopreserved samples resulted positive with direct inoculum method. When the same samples were tested after removal of antibiotic residues, 8 out of 16 (50%) were contaminated. Antibiotic residues present in tissue allografts and processing liquids after decontamination may mask microbial contamination during microbiological analysis performed with standard tissue bank methods, thus resulting in false negatives.

Monitoring the microbial contamination of donor cornea during all preservation phases: A prospective study in the Eye Bank of Rome

“…The standard microbiological analysis detected 11 contaminated TISSUE‐C, and three additional TISSUE‐C samples were found contaminated only when the medium was treated with RESEP for elimination of antimicrobial residues before microbiological testing. Although the automated BACTEC system includes resins that partially remove the antimicrobial agents, these findings underlie the importance of total elimination of antimicrobial residues from the tested sample to avoid false negative results, as also confirmed by other recent reports . The identification of the contaminants detected with the RESEP+ method in the cold storage medium, confirmed the same microbial species as those found without RESEP.…”

“…Although the automated BACTEC system includes resins that partially remove the antimicrobial agents, these findings underlie the importance of total elimination of antimicrobial residues from the tested sample to avoid false negative results, as also confirmed by other recent reports. 21,22 The identification of the contaminants detected with the RESEP+ method in the cold storage medium, confirmed the same microbial species as those found without RESEP.…”

“…However, the antimicrobial efficacy may depend on whether preservation is performed under hypothermic (2‐6°C) or organ culture (31‐37°C) conditions . The possible false negative results that might be obtained during the microbiological testing of samples due to the presence of antibiotic residues in preservation and/or transport media are not always considered . In this prospective study performed at the Italian Eye Bank of Rome, we monitored the contamination rate of 100 donor corneas, and the corresponding identification of the microbial species in each processing step, from tissue recovery to corneal transplantation.…”

Method for sterility testing of corneal storage and transport media after removal of interfering antimicrobials: prospective validation study in compliance with the European Pharmacopoeia

“…Similarly to Buzzi et al , 22 we wanted to verify whether the microbiological positivity observed in the RESEP+ group could have been a consequence of some additional manipulation. However, we excluded this possibility because none of our negative control samples that underwent identical manipulations was found positive for microbial contamination.…”

Gewebe und Zellen – Validierung mikrobiologischer Prüfmethoden bei Verwendung antibiotikahaltiger Medien

“…Es ist auch ein Resinsystem kommerziell erhältlich, in das flüssige, aber auch feste Proben überführt werden können und nach einer Inkubation in diesem System in das mikrobiologische Testsystem überführt werden können (RESEP ® ). Mehrere Studien konnten bereits eine höhere Nachweisrate bei der mikrobiologischen Prüfung unter Verwendung dieses Systems zeigen [5,6].…”