Distinct difference of pancreatic tissue-specific microbiome in autoimmune pancreatitis and pancreatic ductal adenocarcinoma

Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis that may be difficult to distinguish from pancreatic ductal adenocarcinoma (PDAC). Emerging evidence suggests the substantial involvement of gut microbiome dysbiosis in various disorders, including pancreatic diseases. This study investigates the differences in pancreatic tissue-specific microbiomes between AIP and PDAC. Pancreatic tissues were obtained from patients with type 1 AIP (n = 17) or PDAC (n = 24) via ultrasound-guided tissue acquisition and subjected to 16S rRNA sequencing. The sequences were used to determine the bacterial alpha diversity and characterize the microbiome structures related to different sample groups. The pancreatic microbiome in PDAC exhibited increased bacterial alpha diversity compared to that in AIP. The abundances of 16 bacteria were significantly different between the AIP and PDAC groups, and most of them (15/16) were increased in PDAC relative to that in AIP. The bacterial index calculated using these bacteria had a favorable discriminative ability for these different groups, with an area under the curve value of 0.91. Functional analysis demonstrated that the pentose phosphate pathway, gondoate biosynthesis, and several pathways related to adenosine biosynthesis were positively associated with the bacterial index. The findings from this preliminary study indicate that pancreatic microbiome, as a new diagnostic alternative, may potentially help with the differential diagnosis of AIP and PDAC.