Clostridioides difficile R20291 is the most studied PCR-Ribotype 027 isolate. The two predominant lineages of this hypervirulent strain, however, exhibit substantive phenotypic differences and possess genomes that differ by a small number of nucleotide changes. It is important that the source of R20291 is taken into account in research outcomes.
Highlights • Two phenotypically distinct lineages of C. difficile R20291 are in circulation. • Affected are gene transfer, motility, sporulation, biofilm and toxin production. • The differences are due to a small number of single nucleotide genomic changes. • These findings underline the importance of appropriately maintaining stock cultures. • The source of R20291 should be stated in any investigation.