Whole genome sequence analysis reveals limited diversity among Clostridioides difficile ribotype 027 and 078 isolates collected in 22 hospitals in Berlin and Brandenburg, Germany.

BACKGROUND

Clostridioides difficile infections (CDI) present significant health risks and are among the most important nosocomial infections. Ribotype (RT) 027 poses a particular risk due to its proposed "hypervirulence". Traditionally, C. difficile isolates are characterized using PCR-ribotyping. More recently, whole genome sequence (WGS) analysis is increasingly used, which may provide a higher discriminatory power. This study aimed to assess the distribution of different C. difficile RTs in hospitals in the Berlin-Brandenburg area, and to analyse the heterogeneity within isolates of different ribotypes using WGS.

METHODS

Between February 2020 and November 2021, stool samples from patients with laboratory-confirmed CDI were collected from 22 hospitals (approximately 13,900 beds) in Berlin and Brandenburg. Toxigenic isolates (n = 476) were further characterized by ribotyping, antibiotic susceptibility testing, toxinotyping, and core genome multilocus sequence typing (cgMLST).

RESULTS

Sixty-five different RTs were detected, with RT014 (16.1%), RT027 (12.8%), and RT001 (7.6%) being the most prevalent. RT027 isolates exhibited resistance to several antibiotics. Further, cgMLST analysis revealed very close genetic relatedness between RT027 isolates despite being epidemiologically unrelated. Similar findings of a monomorphic population were observed for RT078 isolates. In contrast, other RTs showed a heterogenic population structure.

CONCLUSIONS

This study provides first insights into the distribution of C. difficile genotypes, corresponding antimicrobial resistance, and clonal relatedness using cgMLST, highlighting RT027 as the second most common genotype for the studied area. For the monomorphic RT027 and RT078 populations, new definitions of clonal relatedness might be necessary.