Table 1.

Results from studies investigating bacterial relative abundance in pancreatic tumour patients and pancreatic tumour samples.

Bacterial genera increased in relative abundance	Sites where bacterial genera were increased in relative abundance	Study type and size	Population	Reference
Porphyromonas	Pancreas, Pancreatic duct	189 tissue samples (pancreatic duct, duodenum, pancreas), 57 swabs (bile duct, jejunum, stomach), and 12 stool samples	Case: Caucasian 72 (93.5%), Black 2 (2.6%), Others 2 (2.6%) Control: Caucasian 30 (88%), Black 2 (6%), Others 2 (6%) Cases: Male 38 (49%); Female 39 (51%) Controls: Male 21 (62%); Female 13 (38%)	(Del Castillo et al., 2019)
Fusobacterium, Prevotella, Capnocytophaga, Parvimonas, and Haemophilus	Pancreas
Selenomonas	Pancreas, Duodenum
Gemella	Duodenum
Fusobacterium, Enterobacter, Citrobacter, and Klebsiella	Pancreas	Studied 1526 tumours and their adjacent normal tissues across seven cancer types, including breast, lung, ovary, pancreas, melanoma, bone, and brain tumours. (67 pancreatic tumour tissues)	Biobank	(Nejman et al., 2020)
Fusobacterium	Pancreas	Formalin Fixed, paraffin embedded samples from 17 patients were studied; 9 of whom had pancreatic cancer All 17 had EUS-FNB samples and 6 pancreatic cancer cases had paired resection samples.	Participant numbers listed only	(Masi et al., 2021)
Acinetobacter, Aquabacterium, Oceanobacillus, Rahnella, Massilia, Delftia app., Deinococcus, and Sphingobium	Duodenum	In this study, duodenal mucosal microbiota was analysed in 14 patients with pancreatic head cancer and 14 healthy controls	Participant numbers listed only	(Mei et al., 2018)
Bifidobacterium, Fusobacterium Rothia, Enterococcus, “Escherichia-Shigella”, and Clostridium	Duodenum	Case-control study comparing bacterial and fungal (16S and 18S rRNA) profiles of secretin-stimulated duodenal fluid collections from 308 patients undergoing duodenal endoscopy including 134 normal pancreas control subjects, 98 patients with pancreatic cyst (s) and 74 patients with pancreatic cancer.	Cases: White 57 (90.4%), African American 4 (6.4%), missing 2 (3.2%) Controls: White 57 (90.4%), African American 5 (8%), Missing 1 (1.6%) Cases: Male 40 (63.5%), Female 23 (36.5%) Controls: Male 30 (47.6%), Female 33 (52.4%)	(Kohi et al., 2020)
Porphyromonas, Aggregatibacter, and Alloprevotella	Oral	361 incident adenocarcinoma of pancreas and 371 matched controls were selected from two prospective cohort studies, the American Cancer Society Cancer Prevention Study II and the National Cancer Institute Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.	Cases: White 338 (93.6%), Non-White 23 (6.4%) Controls: White 345 (93.0%), Non-White 26 (7%) Cases: Male 206 (57.1%), Female 155 (42.9%) Controls: Male 212 (57.1%), Female 159 (42.9%)	(Fan et al., 2018)
Actinomyces, Aggregatibacter, Escherichia Lactobacillus, Leptotrichia, Rothia, and Streptococcus	Oral	Prospective study of saliva samples collected from patients with pancreatic cancer (n = 41) and healthy individuals (n = 69).	Cases: Male 24 (59%), Female 17 (41%) Controls: Male 52 (72%), Female 19 (28%)	(Wei et al., 2020)
Cronobacter, Enterobacter, ( Ren et al., 2017) Hallella,  ( Ren et al., 2017) Klebsiella, Prevotella, Selenomonas, and Veillonella	Stool	Prospective study that collected 85 Pancreatic cancer and 57 matched healthy controls to analyze microbial characteristics by MiSeq sequencing	Cases: Male 47 (55.3%); Female 38 (44.7%) Control: Male 36 (63.2); Female 21 (36.8%)	(Ren et al., 2017)