Antimicrobial mixtures used to store harvested skin: antimicrobial activities tested at refrigerator (4 degrees C) temperatures

Risk assessment of arterial allograft contamination from tissue donors colonized by Candida auris

BACKGROUND

Microbiological contamination is one of the main risks that must be controlled in tissue banking practices. For this reason, strict donor selection criteria are applied, disinfection protocols are used, and microbiological monitoring is performed at various stages.

AIM

To detect Candida auris in arterial allografts and assess its origin.

METHODS

Data on two multi-tissue donations with positive microbiological cultures for C. auris were analysed. Risk factors for microbiological contamination were assessed at procurement, processing and post storage.

FINDINGS

C. auris was only isolated in cultures from arteries, and was not detected in cultures from cornea, musculoskeletal tissue or skin (even in the axillary-rectal sample taken from one donor).

CONCLUSION

The donor's own skin was identified as the most likely source to explain the contamination of arteries by C. auris. Due to the pathogenicity of this fungus and difficulties associated with its correct identification, the implementation of measures for its detection in tissue donations is recommended.

Stability analysis of the antibiotic cocktail used by Treviso Tissue Bank Foundation for tissues decontamination

Although careful donor selection reduces tissue contamination, close microbiological control of harvested allografts remains a key task of tissue banks. To guarantee the safety of human tissues for allograft transplantation, a decontamination regimen must be adopted which, as recommended by European guidelines, is active against the majority of microorganisms isolated in tissues. Antibiotic decontamination methods differ from one tissue bank to another in terms of antimicrobial agents, temperature and length of exposure. After identifying the most effective antibiotics against the bacterial strains most commonly isolated in allografts, Treviso Tissue Bank Foundation demonstrated the efficacy of an antibiotic cocktail for tissue decontamination containing Gentamicin, Vancomycin and Meropenem. The aim of this study was to analyse the degradation kinetics of the three antibiotics according to preparation method and use. The results show that only Meropenem is unstable at + 4 °C, while Gentamicin and Vancomycin are valid for over 10 days. We thus established to add Meropenem before the start of the tissue decontamination phase.

Storage media and temperature maintain normal anatomy of cadaveric human skin for transplantation to full-thickness skin wounds

Cadaveric human skin provides an optimal temporary cover after early excision of full-thickness burns; however, engraftment is reduced greatly by cryopreservation. Refrigerated skin is generally preferred because of its rapid revascularization, presumably caused by its greater viability. In this study, the effects of storage solutions, temperature, and the changing of the storage media on skin graft anatomy were evaluated as an indicator of graft viability. Split-thickness human skin grafts (0.012-0.015 mm) were retrieved from cadaveric donors and grafted to circumferential, full-thickness skin wounds on athymic mice. After clinical determination of engraftment 3 months after grafting, 6-mm punch biopsy samples of the human skin were harvested and separated into two groups. Biopsy samples were stored in either saline or Eagle's minimal essential medium. Media were not changed or were changed every 3 days. All groups were stored at either 4 degrees C or room temperature (RT). After 5, 10, and 21 days of storage, biopsy samples were grafted onto athymic mice for 20 days. The biopsy grafts were then collected and prepared for histologic scoring on a scale of +4 (normal anatomy) to 0 (no epithelial cells). Significant differences in histologic scores were found by the nonparametric Kruskal-Wallis test followed by Wilcoxon pairwise comparison. Skin stored in media maintained better histologic anatomy than skin in saline, suggesting better maintenance of viability. There was also better preservation of anatomy after storage at RT for 21 days with media changes every 3 days when compared to unchanged media and all conditions at 4 degrees C. These results support the hypothesis that increased availability of nutrients and increased storage temperature maintain higher viability of cadaveric human skin for transplantation to full-thickness cutaneous wounds.