RT Journal Article SR Electronic T1 A species-wide genetic atlas of antimicrobial resistance in Clostridioides difficile JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.06.14.448453 DO 10.1101/2021.06.14.448453 A1 Korakrit Imwattana A1 César Rodríguez A1 Thomas V. Riley A1 Daniel R. Knight YR 2021 UL http://biorxiv.org/content/early/2021/06/15/2021.06.14.448453.abstract AB Antimicrobial resistance (AMR) plays an important role in the pathogenesis and spread of Clostridioides difficile infection (CDI), the leading healthcare-related gastrointestinal infection in the world. An association between AMR and CDI outbreaks is well documented, however, data is limited to a few ‘epidemic’ strains in specific geographical regions. Here, through detailed analysis of 10,330 publicly-available C. difficile genomes from strains isolated worldwide (spanning 270 multilocus sequence types (STs) across all known evolutionary clades), this study provides the first species-wide snapshot of AMR genomic epidemiology in C. difficile.Of the 10,330 C. difficile genomes, 4,532 (43.9%) in 89 STs across clades 1 – 5 carried at least one genotypic AMR determinants, with 901 genomes (8.7%) carrying AMR determinants for three or more antimicrobial classes (multidrug-resistant, MDR). No AMR genotype was identified in any strains belonging to the cryptic clades. C. difficile from Australia/New Zealand had the lowest AMR prevalence compared to strains from Asia, Europe and North America (p<0.0001). Based on the phylogenetic clade, AMR prevalence was higher in clades 2 (84.3%), 4 (81.5%) and 5 (64.8%) compared to other clades (collectively 26.9%) (p<0.0001). MDR prevalence was highest in clade 4 (61.6%) which was over three times higher than in clade 2, the clade with the second-highest MDR prevalence (18.3%). There was a strong association between specific AMR determinants and three major epidemic C. difficile STs: ST1 (clade 2) with fluoroquinolone resistance (mainly T82I substitution in GyrA) (p<0.0001), ST11 (clade 5) with tetracycline resistance (various tet-family genes) (p<0.0001) and ST37 (clade 4) with macrolide-lincosamide-streptogramin B (MLSB) resistance (mainly ermB) (p<0.0001) and MDR (p<0.0001). A novel and previously overlooked tetM-positive transposon termed Tn6944 was identified, predominantly among clade 2 strains. This study provides a comprehensive review of AMR in the global C. difficile population which may help in the early detection of drug-resistant C. difficile strains, and prevention of spread world-wide.Impact statement Utilising a publicly-available database of 10,330 sequence reads, this study provides the first species-wide evaluation of genotypic AMR in C. difficile. It reports the most common AMR determinants and their genomic neighbourhood, associations between important genotypes and specific strains or geographical regions, and rare AMR genotypes that may have been missed in smaller studies.Data summary This study utilises publicly-available raw sequence reads available at the NCBI Sequence Read Archive (SRA) as of January 2020. The details of all genomes are available in the Supplementary Document (10.6084/m9.figshare.14623533).Competing Interest StatementThe authors have declared no competing interest.