For stem cell patients, keeping a stool in reserve pays off

Researchers have found a way to reverse the damaging effects of broad-spectrum antibiotic treatment on the gut microbiomes of stem cell transplant patients. 

A new study, published in the journal Science Translational Medicine, shows that taking a stool sample prior to treatment and then returning it to the gut afterwards can restore microbial diversity, and may help reduce the risk of future infections. 

The procedure known as allogenic hematopoietic stem cell transplantation (allo-HSCT) is a risky but potentially curative treatment for a variety of blood and bone marrow cancers, such as lymphoma and leukaemia. It is also used to treat a number of non-malignant conditions, including the blood disorders sickle cell anaemia and thalassemia, as well as some autoimmune diseases. 

Allo-HSCT involves replacing a patient’s stem cells with a donor’s healthy ones. As part of the procedure, the patient first undergoes chemotherapy, and possibly radiation therapy, which impairs the ability to produce blood cells. While this sets the stage for the new stem cells, the temporary loss of white blood cells leaves patients highly vulnerable to infection. Thus, as a preventative measure, broad-spectrum antibiotics are routinely administered.{%recommended 3688%}

Unfortunately, these antibiotics kill beneficial bacteria, too, including those that play an important role in the gut microbiome. Paradoxically, this can leave patients more susceptible to future infections, including those by “superbugs” such as vancomycin-resistant Enterococcus and Clostridum difficile. It can also increase the risk of potentially life-threatening graft-versus-host disease.

To address this problem, Ying Taur and Eric Palmer at the Memorial Sloan Kettering Cancer in New York, US, devised a way to restore gut microbial diversity in allo-HSCT patients who receive antibiotic treatment. 

Taur, Palmer and their colleagues first used genetic sequencing to analyse faecal samples taken from a group of allo-HSCT patients who had previously undergone antibiotic treatment, and confirmed that these people experienced a persistent reduction in gut microbial diversity.   

Next, the researchers collected and stored stool samples from a new group of 25 patients who were slated to undergo both allo-HSCT and antibiotic treatment. Following the procedures, 14 of them had their respective stools reintroduced to their intestines, while the remaining 11 received no intervention. 

Over the following year, the research team regularly collected faecal samples from all 25 participants and analysed the microbial composition. They found that those who had received a transplant of their own pre-treatment stool had regained their original gut microbial diversity, while those in the control group did not. 

The researchers are continuing to monitor the patients to see if this restoration of microbial diversity leads to improvements in clinical outcomes, such as a reduction in infections and a decline in graft versus host disease. If so, then “faecal sample banking” could become a very useful clinical tool.