Impact of Bifidobacterium adolescentis in patients with abdominal aortic aneurysm: a cross-sectional study.

The relationships between various diseases and the human gut microbiota (GM) have been revealed. However, the relationships between the human abdominal aortic aneurysm (AAA) and GM remains unknown. The aim of this cross-sectional study was to clarify the association between the human AAA and GM. Stool samples from 30 consecutive patients with AAA before aneurysm repair and those of 30 controls without vascular diseases were analyzed by 16S rRNA gene (V3-4) sequencing using an Illumina MiSeq system and QIIME 2. There was no significant difference in age (75 vs. 75 years) or gender (80% vs. 87% males) between the groups. No significant difference in GM composition was observed in principal coordinate analysis between the two groups, whereas the AAA group showed a significantly lower abundance of Bifidobacterium adolescentis (p<0.01) at the species level than the controls. This study demonstrated that the abundance of B. adolescentis decreased in patients with AAA. This is the first study to show the characteristics of the GM in patients with AAA. Studies are needed to reveal if causal relationships exists between the human AAA and GM.