Inflammation plays a part in the development of abdominal aortic aneurysm (AAA), and
the gut microbiota affects host inflammation by bacterial translocation. The relationship
between abdominal aortic aneurysm and the gut microbiota remains unknown. This study
aimed to detect bacterial translocation in the aneurysmal wall and blood of patients
with abdominal aortic aneurysm, and to investigate the effect of the gut microbiota
on abdominal aortic aneurysm. We investigated 30 patients with abdominal aortic aneurysm
from 2017 to 2019. We analysed the aneurysmal wall and blood using highly sensitive
reverse transcription-quantitative polymerase chain reaction, and the gut microbiota
was investigated using next-generation sequencing. In the 30 patients, bacteria were
detected by reverse transcription- quantitative polymerase chain reaction in 19 blood
samples (detection rate, 63%) and in 11 aneurysmal wall samples (detection rate, 37%).
In the gut microbiota analysis, the Firmicutes/Bacteroidetes ratio was increased.
The neutrophil-lymphocyte ratio was higher (2.94 +/- 1.77 vs 1.96 +/- 0.61, P < 0.05)
and the lymphocyte-monocyte ratio was lower (4.02 +/- 1.25 vs 5.86 +/- 1.38, P < 0.01)
in the bacterial carrier group than in the bacterial non-carrier group in blood samples.
The volume of intraluminal thrombus was significantly higher in the bacterial carrier
group than in the bacterial non-carrier group in aneurysmal wall samples (64.0% vs
34.7%, P < 0.05). We confirmed gut dysbiosis and bacterial translocation to the blood
and aneurysmal wall in patients with abdominal aortic aneurysm. There appears to be
a relationship between the gut microbiota and abdominal aortic aneurysm.