Certain Bacteria May Build Organ Tolerance in Lung Transplant Patients

New research evaluates how microbes interact with and respond to transplanted lungs

MONTREAL, April 25, 2013 – New research will be revealed today at the International Society for Heart and Lung Transplantation (ISHLT) 33rd Annual Meeting and Scientific Sessions in Montreal, Canada to determine if there is a link between microbiota (microscopic living organisms of a region) and the development of transplant complications, especially chronic rejection.  Results indicate the nasopharynx (rear of the nasal cavity) serves as a reservoir for bacteria that can infect the newly transplanted lung.

The initial study explored the relationship between the bacteria in the lungs and bronchiolitis obliterans syndrome (BOS) in a group consisting mainly of Cystic Fibrosis (CF) lung transplant patients.  According to the Cystic Fibrosis Foundation about 750 to 1,000 individuals with CF have received lung transplants in the past five years.  BOS represents rejection of the transplanted lungs which is the main cause of death after  the first year post-transplant.

The results indicated that in CF patients, a high level of Pseudomonas, the most common CF pathogen, was not associated with BOS.  Contrary to traditional belief, a re-establishment of Pseudomonas in lungs post-transplant had a protective effect.  This phenomenon occurred to a lesser extent in non-CF patients and with other types of bacteria suggesting that transplant patients can exhibit tolerance to bacteria present in the lungs even if they are known respiratory pathogens.

“The results are intriguing to say the least, one could speculate that tolerance to these ‘good’ bugs may prevent infection with ‘bad bugs’ and even facilitate tolerance to the transplanted organ as well,” according to Daniel Chambers, M.B., B.S. (Hons), Member of the Royal College of Physicians, Fellow of the Royal Australasian College of Physicians, a transplant physician at The Prince Charles Hospital in Brisbane, Australia, and the lead clinician for this research. 

Dana Willner, M.S., Ph.D., a research fellow at the Australian Centre for Ecogenomics, who led this study further elaborated that, “Past research shows us that the ‘good’ bugs found in the rest of the body are essential to human health, and similar relationships may exist in the lung as indicated by our study.”

Bacterial Communities

Researchers observed how the bacterial communities in the lungs changed over time.

The amount of bacteria fluctuated in response to antibiotic pressure but eventually stabilized over time. For a sub-set of patients, how microbes in certain body sites (nasopharynx, mouth and gut) interact with and respond to the transplanted lungs were also evaluated.

In CF patients and non-CF patients, the nasopharynx was a vital reservoir for bacteria. While the mouth and gut were both sources for bacteria, gut communities were notably distinct and more specific to individuals rather than pre-transplant conditions or transplant outcomes.

The study concludes that microbial communities remote from the lung interact with respiratory microbiota and the immune system and should be considered holistically. The study calls for re-examination of current methods for treating respiratory tract infections. Current methods include microbial eradication, however in light of today’s research that approach may be ineffective and inappropriate.

The International Society for Heart and Lung Transplantation (ISHLT) is a not-for-profit professional organization with more than 2,700 members from over 45 countries dedicated to improving the care of patients with advanced heart or lung disease through transplantation, mechanical support and innovative therapies via research, education and advocacy. For more information, visit www.ishlt.org.

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