GI flora in GVHD

 A note on the role of Gastrointestinal Flora in Graft vs Host Disease (GVHD) 

There is a continuous and an increased interest on the role lower gastrointestinal (GI) tract bacterial microbiome plays in the development of GVHD. It is proposed that by modifying GI bacterial flora in peri-transplant period, GVHD can be prevented - as GVHD has been found to be associated with the increase pro-inflammatory bacteria, decrease anti-inflammatory bacteria, and less bacterial diversity in GI tract. 

At least one recent study comprising of 8767 fecal samples from 1362 patients undergoing allogeneic hematopoietic-cell transplantation at four major centers showed that alterations of the lower GI microbiome i.e., loss of diversity is associated with increased mortality from GVHD  4. Some preliminary work (disclaimer: weak evidence) shows that prophylactic use of quinolone may help in preventing GVHD. This prophylactic quinolone (like ciprofloxacin) can be started a day prior to the initiation of the preparatory regimen and continue till patient is engrafted or started on IV antibiotics.

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References:

1. Taur Y, Jenq RR, Perales MA, et al. The effects of intestinal tract bacterial diversity on mortality following allogeneic hematopoietic stem cell transplantation. Blood 2014; 124:1174. 

2. Holler E, Butzhammer P, Schmid K, et al. Metagenomic analysis of the stool microbiome in patients receiving allogeneic stem cell transplantation: loss of diversity is associated with use of systemic antibiotics and more pronounced in gastrointestinal graft-versus-host disease. Biol Blood Marrow Transplant 2014; 20:640. 

3. Beelen DW, Elmaagacli A, Müller KD, et al. Influence of intestinal bacterial decontamination using metronidazole and ciprofloxacin or ciprofloxacin alone on the development of acute graft-versus-host disease after marrow transplantation in patients with hematologic malignancies: final results and long-term follow-up of an open-label prospective randomized trial. Blood 1999; 93:3267. 

4. Peled JU, Gomes ALC, Devlin SM, et al. Microbiota as Predictor of Mortality in Allogeneic Hematopoietic-Cell Transplantation. N Engl J Med 2020; 382:822.