Colonization with Murine pks+ Escherichia coli under Non-Inflammatory Conditions

pks+ Escherichia coli is increasingly implicated in the development of colorectal cancer (CRC), particularly among a rapidly expanding subset of younger patients with early-onset CRC. pks+ E. coli strains produce the genotoxin colibactin, known to cause double-strand DNA breaks and mutations in cell proliferation and differentiation pathways associated with CRC. This article details a method for pks+ E. coli colonization in mice under non-inflammatory conditions, from preparation of bacterial inoculum through to validation of colonization. Following overnight incubation, pks+ E. coli strain E. coli NC101 is administered to antibiotic-conditioned mice via oral gavage. Colonization is assessed in stool by quantifying the number of lactose-fermenting gram-negative colony forming units (CFUs) and by quantitative PCR amplification. Using this protocol, it was shown that, following the successful colonization of C57BL/6 mice with E. coli NC101, supplementation with the dietary fiber inulin promoted the growth of pks+ E. coli, reflected by increased recovery of CFUs, higher abundance of the Enterobacteriaceae family, and increased levels of the clbP gene. In summary, this model allows for the study of preventative and therapeutic treatments targeting a key pathobiont involved in CRC development.