Experts have long observed that those with poor oral health are more vulnerable to pancreatic cancer than those with healthier mouths. The researchers had also conducted a small study in 2016 that tied microbes living in the mouth to pancreatic cancer, but could not identify precise bacterial species. The data were gathered for the American Cancer Society Cancer Prevention Study II and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Then, they identified 445 patients who were diagnosed with pancreatic cancer and compared the DNA of their microbes with that of another 445 randomly selected study subjects who had remained cancer free. The findings identified 24 species of bacteria and fungi that individually either raised or lowered pancreatic cancer risk.