Characterization of Escherichia coli harboring colibactin genes (clb) isolated from beef production and processing systems

Authors: Guragain, Manita; Schmidt, John; Kalchayanand, Norasak - Nor; Dickey, Aaron; Bosilevac, Joseph - Mick

Submitted to: Nature Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2022
Publication Date: 3/29/2022
Citation: Guragain, M., Schmidt, J.W., Kalchayanand, N., Dickey, A.M., Bosilevac, J.M. 2022. Characterization of Escherichia coli harboring colibactin genes (clb) isolated from beef production and processing systems. Nature Scientific Reports. 12. Article 5305. https://doi.org/10.1038/s41598-022-09274-x.
DOI: https://doi.org/10.1038/s41598-022-09274-x

Interpretive Summary: Some E. coli produce a toxin called colibactin that can lead to colorectal cancer in people. Since E. coli can be found on red meat and red meat diets have been associated with colorectal cancer, we examined E. coli isolated from cattle, beef products, and points along the beef production chain. E. coli that produce colibactin were found in cattle and on beef. Current beef interventions were shown to be effective at reducing these E. coli on beef. The presence of these E. coli on beef may be confounding the association of colorectal cancer and red meat, and further studies are needed. These data indicate that certain beef associated E. coli could be the cause of colorectal cancer in beef consumers rather than the beef per se.

Technical Abstract: Certain strains of Escherichia coli possess and express the toxin colibactin (Clb) which induces host mutations identical to the signature mutations of colorectal cancer (CRC) that lead to tumorigenic lesions. Since cattle are a known reservoir of several Enterobacteriaceae including E. coli, this study screened for clb amongst E. coli isolated from colons of cattle-at-harvest (entering beef processing facility; n'='1430), across the beef processing continuum (feedlot to finished subprimal beef; n'='232), and in ground beef (n'='1074). Results demonstrated that clb+ E. coli were present in cattle and beef. Prevalence of clb+ E. coli from colonic contents of cattle and ground beef was 18.3% and 5.5%, respectively. clb+ E. coli were found susceptible to commonly used meat processing interventions. Whole genome sequencing of 54 bovine and beef clb+ isolates showed clb occurred in diverse genetic backgrounds, most frequently in phylogroup B1 (70.4%), MLST 1079 (42.6%), and serogroup O49 (40.7%).