Differentiating virulent 027 and non-027 Clostridium difficile strains by molecular methods

Objective: Hypervirulent Clostridium difficile clade has been shown to include several lineages of ribotype 027 and also other ribotypes. We present data on additional non-027 strains, identified as presumptive 027 by two commercial molecular C. difficile assays. Methods: The tested clinical isolates were selected from the national reference laboratory collection on the basis of toxin gene profile similarities with ribotype 027 and tested with Xpert (R) C. difficile/Epi and Amplidiag (TM) C. difficile+027 assay. Result: Xpert misclassified five ribotypes (016, 019, 080, 176 and variant of type 046) as presumptive 027 and Amplidiag two ribotypes (016, 176). The misclassified strains were rare, covering 1.6% of reference laboratory strain collection. Conclusion: Our findings confirm the concept that there are closely related outliers to hypervirulent 027 clones that can be misclassified as 027, and that these comprise numerous ribotypes, including previously reported four ribotypes (198, 176, 244, 019), and additional three (016, v046, 080) identified in the present study.