<i>Clostridioides difficile</i> antibody response of colorectal cancer patients versus clinically healthy individuals

Dysbiosis, defined as an imbalance in the gut microbiota caused by too few beneficial bacteria and an overgrowth of bad bacteria, yeast, and/or parasites, is now being associated with several diseases, including the development of colorectal carcinoma (CRC). In this study, the potential association of <i>Clostridioides difficile</i> (formerly <i>Clostridium difficile</i>) with CRC was investigated. Plasma samples obtained from preoperative histologically confirmed CRC patients (<i>n</i>=39) and their age- and sex-matched clinically healthy controls (<i>n</i>=39) were analyzed for antibodies to toxin B of <i>C. difficile</i> (anti-tcdB) by enzyme-linked immunosorbent assay (ELISA). A significantly greater number (p=0.012) of CRC cases (<i>n</i>=26/39, 66.7%) had anti-tcdB IgG levels above the cutoff value compared with controls (<i>n</i>=12/39, 30.8%). Eight cases (8/39, 20.5%) and none of the controls registered anti-tcdB IgA levels above the cutoff value (p=0.0039). Anti-tcdB IgG and IgA levels were not shown to be significantly associated with tumor grade or tumor stage. Anti-tcdB IgG showed 66.7% sensitivity and 69.2% specificity. For anti-tcdB IgA, sensitivity and specificity were 20.5% and 100%, respectively. The positive predictive values for anti-tcdB IgA and IgG were 100% and 68.4%, respectively. The anti-tcdB IgA and IgG negative predictive values were 55.7% and 67.5%, respectively. The results suggest the potential association of <i>C. difficile</i> with CRC and anti-tcdB levels, particularly the IgA level. Hence, anti-tcdB antibodies can be candidate serologic markers for CRC.