Assessment of Genotoxic <em>Escherichia coli</em> and <em>Helicobacter pylori</em> Pathogenicity in the Context of Gastrointestinal Carcinogenesis in a Turkish Cohort

Gastrointestinal cancer is defined as the second leading cause of cancer related deaths in the world. In addition to many environmental and hereditary factors that cause cancer, recent studies have shown that many types of microorganisms can also cause cancer due to chronic infections, virulence factors and carcinogenic metabolites. Helicobacter pylori play a pivotal role in the initiation of gastric carcinogenesis, whereas Escherichia coli has been implicated in the progression of colorectal cancer. The aim of this research is to get more detailed information about the gastrointestinal cancer associated pathogens, to define the role of genotoxin producing Escherichia coli for the colon cancer and Helicobacter pylori virulence factors in Turkish population. For the purpose of this study, tumor tissue specimens were collected from patients diagnosed with colon and gastric cancer. In colon tumor tissues, the presence of colibactin was assessed by screening for the genes clbA, clbB, clbN, and clbQ. In gastric tumor tissues, Helicobacter pylori virulence factors including ureA, ureB, dupA, hpaA, napA, cagA, and vacA (s1/s2) were analyzed. Colibactin positivity (clb+) was detected in only four colon cancer patients, while H. pylori virulence factors were identified in three gastric cancer patients. Two clb+ colon tumor samples were cultured using the single-colony isolation technique. Whole-genome sequencing (WGS) was subsequently performed on isolates from these cultures to determine their species identity. The first sample yielded Escherichia coli Nissle, while the second was identified as Citrobacter braakii.