Antibody response to enterotoxigenic Bacteroides fragilis of Filipino colorectal cancer patients.

Background: Several species of the gut microbiota have been implicated in colorectal cancer (CRC) development. The anaerobic bacterium enterotoxigenic Bacteroides fragilis (ETBF), has been identified to produce fragilysin, a toxin known to cleave E-cadherin, thereby leading to carcinogenesis. Objective: To determine the antibody response of CRC patients against ETBF to ascertain whether significant difference exists or whether antibody response is related to tumor grade and tumor stage. Methods: Informed consent was obtained from histologically confirmed CRC casesand their age- and sex-matched clinically healthy controls. Plasma samples from the participants were subjected to in-house enzyme-linked immunosorbent assay (ELISA) to determine their antibody levels. Results: Using ETBF total protein as coating antigen, 38/39 (97%) CRC cases and 36/39 (92%) controls showed anti-ETBF IgG above cut-off, while all (100%) CRC cases and 36/39 (92%) controls had anti-ETBF IgA levels above cut-off. With culture broth as coating antigen, all (100%) CRC cases and 37/39 (95%) controls had anti-ETBF IgG levels above cut-off. For anti-ETBF IgA, all (100%) cases and controls had levels above cut-off. Statistical analysis reveals no significant difference (P > 0.05) on the number of CRC cases and controls with IgG and IgA antibody levels above cut-off value. Also, there's no significant difference (P > 0.05) in the mean anti-ETBF antibody levels of cases who were at different tumor grade (well differentiated and moderately and poorly differentiated) and tumor stage (early and advanced). Conclusions: These results suggest that Filipino CRC cases and their clinically healthy matched controls exhibit antibody responses against ETBF.

pks+ Escherichia coli more prevalent in benign than malignant colorectal tumors.

BACKGROUND: Some E. coli strains that synthesize the toxin colibactin within the 54-kb pks island are being implicated in colorectal cancer (CRC) development. Here, the prevalence of pks+ E. coli in malignant and benign colorectal tumors obtained from selected Filipino patients was compared to determine the association of pks+ E. coli with CRC in this population. METHODS AND RESULTS: A realtime qPCR protocol was developed to quantify uidA, clbB, clbN, and clbA genes in formalin fixed paraffin embedded colorectal tissues. The number of malignant tumors (44/62; 71%) positive for the uidA gene was not significantly different (p = 0.3428) from benign (38/62; 61%) tumors. Significantly higher number of benign samples (p < 0.05) were positive for all three colibactin genes (clbB, clbN, and clbA) compared with malignant samples. There was also higher prevalence of pks+ E. coli among older females and in tissue samples taken from the rectum. CONCLUSION: Hence, pks+ E. coli may not be associated with CRC development among Filipinos.

Clostridioides difficile 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 Clostridioides difficile (formerly Clostridium difficile) with CRC was investigated. Plasma samples obtained from preoperative histologically confirmed CRC patients (n=39) and their age- and sex-matched clinically healthy controls (n=39) were analyzed for antibodies to toxin B of C. difficile (anti-tcdB) by enzyme-linked immunosorbent assay (ELISA). A significantly greater number (p=0.012) of CRC cases (n=26/39, 66.7%) had anti-tcdB IgG levels above the cutoff value compared with controls (n=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 C. difficile with CRC and anti-tcdB levels, particularly the IgA level. Hence, anti-tcdB antibodies can be candidate serologic markers for CRC.