Declaration of personal and funding interests: None

This letter refers to the paper “Nooij S, Ducarmon QR, Laros JFJ, Zwittink RD, Norman JM, Smits WK, Verspaget HW, Keller JJ, Terveer EM, Kuijper EJ; working group of the Netherlands Donor Feces Bank. Faecal microbiota transplantation influences procarcinogenic Escherichia coli in recipient recurrent Clostridioides difficile patients. Gastroenterology. 2021 Jun 11:S0016-5085(21)03120-6. https://doi.org/10.1053/j.gastro.2021.06.009. Epub ahead of print. PMID: 34126062 (Corresponding author: Sam Nooij, Leiden University Medical Center, department of Medical Microbiology, P.O. box 9600, post zone E4-P, 2300 RC Leiden, the Netherlands; [email protected] ).