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.