Could gut microbiota be the culprit?

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Science Translational Medicine  02 Mar 2016:
Vol. 8, Issue 328, pp. 328ec38
DOI: 10.1126/scitranslmed.aaf3858

Pulmonary complications are among the most common causes of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HCT). Although there are several established post-HCT pulmonary complications, little is known about the factors predisposing HCT patients to developing lung pathology. Harris and colleagues set out to investigate the relationship between the bacterial composition of the gut and the development of post-HCT pulmonary complications by conducting an observational study of HCT patients at a single transplant center.

The investigators recruited 94 HCT patients previously enrolled in a study involving the genetic sequencing of the gut microbiota and reviewed data for 40 months post-HCT looking for pulmonary complications. The study group defined “pulmonary complications” as any new pulmonary infiltrate on chest imaging in the setting of respiratory complaints or abnormal vital signs. In total, 112 post-HCT pulmonary events were documented in 66 (70.2%) of the 94 HCT patients recruited. Analysis of the gut microbiota data revealed that individuals with a gut microbiota that was dominated by γ-Proteobacteria were more likely to develop post-HCT pulmonary complications and showed a trend towards significance for mortality. Based on these results, the investigators concluded that a relationship exists between the gut microbiota and post-HCT pulmonary complications.

The limitations of this study include the fact that the gut microbiome was analyzed after admission for the transplant but prior to the development of the pulmonary pathology, thus making the link between the gut microbiome and lung pathology less convincing. Also, the broad definition used to identify cases with post-HCT pulmonary complications potentially biased the study’s conclusions. In addition, the study group consisted of a relatively small sample of individuals from a single institution, limiting the generalizability of the data.

B. Harris et al., Gut microbiota predict pulmonary infiltrates after allogeneic hematopoietic cell transplantation. Am. J. Respir. Crit. Care Med. 10.1164/rccm.201507-1491OC (2016). [Abstract]

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