RT Journal Article SR Electronic T1 The oral microbiota in colorectal cancer is distinctive and predictive JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP gutjnl-2017-314814 DO 10.1136/gutjnl-2017-314814 A1 Burkhardt Flemer A1 Ryan D Warren A1 Maurice P Barrett A1 Katryna Cisek A1 Anubhav Das A1 Ian B Jeffery A1 Eimear Hurley A1 Micheal O’Riordain A1 Fergus Shanahan A1 Paul W O’Toole YR 2017 UL http://gut.bmj.com/content/early/2017/10/07/gutjnl-2017-314814.abstract AB Background and aims Microbiota alterations are linked with colorectal cancer (CRC) and notably higher abundance of putative oral bacteria on colonic tumours. However, it is not known if colonic mucosa-associated taxa are indeed orally derived, if such cases are a distinct subset of patients or if the oral microbiome is generally suitable for screening for CRC.Methods We profiled the microbiota in oral swabs, colonic mucosae and stool from individuals with CRC (99 subjects), colorectal polyps (32) or controls (103).Results Several oral taxa were differentially abundant in CRC compared with controls, for example, Streptococcus and Prevotellas pp. A classification model of oral swab microbiota distinguished individuals with CRC or polyps from controls (sensitivity: 53% (CRC)/67% (polyps); specificity: 96%). Combining the data from faecal microbiota and oral swab microbiota increased the sensitivity of this model to 76% (CRC)/88% (polyps). We detected similar bacterial networks in colonic microbiota and oral microbiota datasets comprising putative oral biofilm forming bacteria. While these taxa were more abundant in CRC, core networks between pathogenic, CRC-associated oral bacteria such as Peptostreptococcus, Parvimonas and Fusobacterium were also detected in healthy controls. High abundance of Lachnospiraceae was negatively associated with the colonisation of colonic tissue with oral-like bacterial networks suggesting a protective role for certain microbiota types against CRC, possibly by conferring colonisation resistance to CRC-associated oral taxa and possibly mediated through habitual diet.Conclusion The heterogeneity of CRC may relate to microbiota types that either predispose or provide resistance to the disease, and profiling the oral microbiome may offer an alternative screen for detecting CRC.