Sources and prevention of graft infection during long‐term ex situ liver perfusion

Abstract

Introduction The use of normothermic liver machine perfusion to repair injured grafts ex situ is an emerging topic of clinical importance. However, a major concern is the possibility of microbial contamination in the absence of a fully functional immune system. Here, we report a standardized approach to maintain sterility during normothermic liver machine perfusion of porcine livers for one week. Methods Porcine livers (n = 42) were procured and perfused with blood at 34°C following aseptic technique and standard operating procedures. The antimicrobial prophylaxis was adapted and improved in a step‐wise manner taking into account the pathogens that were detected during the development phase. Piperacillin‐Tazobactam was applied as a single dose initially and modified to continuous application in the final protocol. In addition, the perfusion machine was improved to recapitulate partially the host's defense system. The final protocol was tested for infection prevention during one week of perfusion. Results During the development phase, microbial contamination occurred in 27 out of 39 (69%) livers with a mean occurrence of growth on 4 ± 1.6 perfusion days. The recovered microorganisms suggested an exogenous source of microbial contamination. The antimicrobial agents (piperacillin/tazobactam) could be maintained above the targeted minimal inhibitory concentration (8‐16 mg/L) only with continuous application. In addition to continuous application of piperacillin/tazobactam, partial recapitulation of the host immune system ex situ accompanied by strict preventive measures for contact and air contamination maintained sterility during one week of perfusion. Conclusion The work demonstrates feasibility of sterility maintenance for one week during ex situ normothermic liver perfusion.

Normothermic Ex Vivo Liver Platform Using Porcine Slaughterhouse Livers for Disease Modeling

“…However, during short-term (5 h) perfusion, the effect of infections is expected to be limited, and no pockets of infections were shown by histology. Nevertheless, to reach long-term perfusion, the addition of antibiotics is necessary [ 39 ], and future research should focus on the risk of bacterial infections due to slaughterhouse harvesting.…”

Long-term normothermic machine preservation of human livers: what is needed to succeed?

“…Eshmuminov et al also explored the best preventative strategy during 7-day NMP and found microbial contamination, mostly from an external source, probably due to operating the perfusion machine. They also showed that continuous infusion of piperacillin-tazobactam was preferred over a daily bolus to maintain a stable concentration (101).…”

“…The most common organisms seen during ECMO are coagulase-negative staphylococci, Candida spp., P. aeruginosa, S. aureus, Enterococcus, Enterobacter spp., and S. maltophilia, which are also common organisms for the majority of the non-ECMO device and procedure-related healthcare-associated infections and were also found during 7-day liver perfusions (101,104,105). Fungal infections are not often seen.…”

Bacterial and Viral Infections in Liver Transplantation: New Insights from Clinical and Surgical Perspectives

“…For these reasons, the use of antibiotics during NMP of the liver is well established and has been a part of each group’s clinical protocol. In the development phase of the study of Eshmuminov et al [ 106 ], microbial contamination occurred in 69% of porcine livers with a mean occurrence of growth on 4 ± 1.6 perfusion days. So, they switched the antimicrobial infusion in a continuous application, reduced the perfusate sampling and avoided taking liver biopsies; as a result, no more microbiological growth was observed perfusing the livers ex situ up to 1 week.…”