Nebulized antibiotics for pulmonary infections in an ex vivo lung perfusion (EVLP) lamb model: a feasibility pilot study

infection lung transplantation Ex vivo lung perfussion

Dr. M.E. Erasmus
Tji Gan
O. Akkerman
D. Touw
L. Venema

Nature of the research:
pre clinical research in an ex vivo lung perfusion lamb model

Fields of study:
pharmacology pulmonology microbiology

Background / introduction
Lung transplantation is a definite option in end-stage lung disease. However patients
still die awaiting a lung transplantation due to donor organ shortage. Approximately 20% of the patients die on the lung transplantation waitlist. Ideally, a potential lung donor is younger
than 45 years, has a good gas exchange with a PO2/FIO2 > 350mmHg (40kPa), has never smoked,
a negative bacterial culture, a clear appearance on bronchoscopy, and normal chest-x-ray (Bothas Transplantation 2006). However, lung transplant physicians and surgeons phase the fact that there is no such thing as an ideal donor. As a consequence liberalization of the standard donor criteria has occurred to increase donor organ availability. An extended ‘marginal’ donor is referred to as a donor age < 55 years, and/or smoking history of < 20 pack years, and/or a PO2/FIO2< 350mmHg (40kPa).

Our own data from the UMCG transplant program has shown that annually approximately 20% of the potential donor lungs offered are declined because of signs of a respiratory infection; i.e pneumonia. Recent medical technical developments in transplant medicine has shown that ex vivo lung perfusion (EVLP) is a platform to evaluate, recondition and treat potential donor lungs.
The donor organ pool might be increased by accepting infectious donor lungs,
treating them and possibly implanting them. There is scarce data on treatment of pulmonary infections in EVLP. Pre- and clinical data has shown that infectious donor lungs can be treated by administration of antibiotics to the perfusion fluid on EVLP (Nakajima Am J Tranplant 2016, Andreasson J Heart Lung Transplant 2014). However, local endobronchial antibiotic concentrations, the effect on bacterial load and 16srRNA in bronchial washing, and the comparison between the different administration routes has not been investigated previously.
The research described in this application aims to investigate, in an EVLP infectious lamb lung model, whether nebulized antibiotic therapy can reach effective local concentration, and assess
the effect on bacterial load and 16srRNA.

The pilot data from the research described in this grant application will form the base for a translational study in clinical EVLP yet to be initiated, where nebulized antibiotics will be administrated in infectious donor lungs. Stretching the marginal donor criteria by accepting infectious donor lungs, and treating with nebulized antibiotics potentially increases
the donor pool and possibly result in more lung transplantations and less deaths on the transplantation waitlist.
Research question / problem definition
The three main objectives of this research proposal are:
1. Treatment of a respiratory infection by administration of antibiotics via perfusion fluid and compare to treatment with nebulized antibiotics in an EVLP infectious lamb model.
2. Measure local endobronchial concentrations of antibiotics in the endobronchial lining fluid with both administrations; i.e via perfusion fluid and nebulized.
3. Evaluate the treatment effects of nebulized antibiotics and antibiotics via perfusion fluid by determining bacterial load and 16srRNA in bronchial washing
The research will be conducted in our operational EVLP lamb model. The lamb lungs on EVLP will be transfected with Pseudomonas aeruginosa. Treatment of the respiratory infection with either nebulized or systemic antibiotics, or both will be investigated on EVLP. During treatment on EVLP local concentrations of antibiotics will be measured. Bacterial load and 16srRNA will be assessed in broncho-alveolar lavage.

Detailed workplan
Death after circulatory death (DCD) lamb lungs will be obtained from a local butchery/slaughterhouse and prepared for EVLP according to our local protocol. After a stable period of 1 hour of EVLP with the standard EVLP parameters within a stable range, an infection with Pseudomonas aeruginosa will be introduced in the middle lobe. There will be 4 EVLP lambgroups (total n= 20) :
1. Control group (n= 5); with standard perfusion fluid + nebulized NaCl 0.9%.
2. Group 1 (n= 5); Standard perfusion + Tobramycine + nebulized NaCl 0.9%.
3. Group 2 (n= 5); Standard perfusion + nebulized Tobramycine
4. Group 3 (n= 5); Standard perfusion + Tobramycine + nebulized Tobramycine
In each group after 3 and 6 hours of perfusion Tobramycine concentrations will be assessed in the perfusion fluid and in the pulmonary epithelial lining fluid at the side of infection in samples taken by bronchoalveolar lavage.
Before and after 3 and 6 hours of perfusion quantitative cultures of bacteria will be performed on broncho-alveolar lavage fluid from the EVLP lamb lungs. In addition, 16srRNA will be assessed in the broncho-alveoalr lavage fluid The identification of Pseudomonas aeruginosa or any organisms, and changes in number of colony forming units before and after EVLP will be assessed.
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