What is already known
Organ transplants are life-saving procedures, but they carry a high risk of organ rejection, infections and mortality. Some studies suggested that stem cell transplants are linked to harmful alterations in the recipients’ gut microbiota, but it’s unclear whether this also occurs after solid organ transplant.
What this research adds
To study how the gut microbiota changes after solid organ transplant, researchers analyzed more than 1,300 stool samples from hundreds of people who had either a liver or a kidney transplant. They also followed some kidney transplant recipients for up to two years after the transplant. Overall, transplant recipients experienced changes in their gut bacteria, including a less diverse microbiota and a higher prevalence of harmful species and genes linked to antibiotic resistance. People with the lowest bacterial diversity also had poorer survival rates than those with high bacterial diversity. Drugs that weaken the immune system — which are routinely used to prevent organ rejection — were the main driving factor of microbiota disruptions.
Conclusions
The findings suggest that microbiota-based therapies can help improve clinical outcomes after organ transplants.
Organ transplants are life-saving procedures, but they carry a high risk of organ rejection, infections and mortality. New research shows that some transplant recipients experience changes in their gut bacteria that are associated to poorer survival after transplantation.
The findings, published in Science Translational Medicine, suggest that microbiota-based therapies can help improve clinical outcomes after organ transplants.
Previous studies have shown that stem cell transplants are linked to harmful alterations in the recipients’ gut microbiota, but it’s unclear whether this also occurs after solid organ transplant.
To study how the gut microbiota changes after solid organ transplant, Casper Swarte, Rinse Weersma at University Medical Center Groningen and their colleagues set out to analyze stool samples from people who had either a liver or a kidney transplant.
Microbiota disruption
The researchers collected and analyzed 1,370 stool samples from 415 recipients of liver transplants and 672 recipients of kidney transplants. They also analyzed samples from 1,183 controls, and followed 78 of the kidney transplant recipients for two years after the transplant.
Overall, transplant recipients experienced changes in their gut bacteria, including a less diverse microbiota. For example, the abundance of many commensal species such as Akkermansia muciniphila and Ruminococcus obeum were decreased after transplantation, whereas species such as Clostridium asparagiforme and Coprobacter fastidiosus were more abundant after transplantation.
Some transplant recipients also had a higher prevalence of harmful species in their guts as well as genes linked to antibiotic resistance. Some of these alterations persisted for up to 20 years after transplantation, the researchers found.
Poorer outcomes
People with the lowest bacterial diversity in their guts had poorer survival rates than those with higher bacterial diversity. The team found that 77% of people with low bacterial diversity survived three years after transplantation compared with 96% of those with high bacterial diversity.
Further analyses showed that drugs that weaken the immune system — which are routinely used to prevent organ rejection — were the main driving factor of microbiota disruptions.
Although the study doesn’t include recipients of other solid transplants such as heart and lung transplants, the findings “represents an important step toward potential future microbiome-targeted interventions that could influence the outcomes of recipients of solid organ transplantation,” the authors say. Future work, they add, should also demonstrate a causal link between microbiota disruptions and poorer survival in transplant recipients.
