The presence of oral bacteria in cystic pancreatic tumours is associated with the severity of the tumour, a new study suggests.

According to the researcher, the results can help to reappraise the role of bacteria in the development of pancreatic cysts. If further studies show that the bacteria actually affects the pathological process, it could lead to new therapeutic strategies using antibacterial agents.

"We were surprised to find oral bacteria in the pancreas, but it wasn't totally unexpected. The bacteria we identified has already been shown in an earlier, smaller study to be higher in the saliva of patients with pancreatic cancer," said co-author Margaret Sallberg Chen from the Karolinska Institutet in Sweden.

Not all pancreatic tumours are cancerous. For instance there are so-called cystic pancreatic tumours (pancreatic cysts), many of which are benign. A few can, however, become cancerous, the researcher said. "We find most bacteria at the stage where the cysts are starting to show signs of cancer," Chen said.

"What we hope is that this can be used as a biomarker for the early identification of the cancerous cysts that need to be surgically removed to cure cancer..." she added.

For the study, published in the journal Gut, the team examined the presence of bacterial DNA in fluid from pancreatic cysts in 105 patients and compared the type and severity of the tumours. The results showed that the fluid from the cysts with high-grade dysplasia and cancer contained much more bacterial DNA than that from benign cysts.

To identify the bacteria, the researchers sequenced the DNA of 35 of the samples that had high amounts of bacterial DNA. They found large variations in the bacterial composition between different individuals, but also a greater presence of certain oral bacteria in fluid and tissue from cysts with high-grade dysplasia and cancer.