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

Area of Science:

• Clinical microbiology
• Molecular diagnostics
• Infectious diseases

Background:

• Hypervirulent Clostridium difficile (C. diff) clade includes ribotype 027 lineages and other ribotypes.
• Accurate identification of C. diff strains is crucial for effective treatment and infection control.

Purpose of the Study:

• To evaluate the accuracy of two commercial molecular assays in identifying hypervirulent C. diff ribotype 027.
• To identify non-027 C. diff strains misclassified as presumptive 027 by these assays.

Main Methods:

• Clinical isolates with toxin gene profiles similar to ribotype 027 were selected.
• Isolates were tested using Xpert C. difficile/Epi and Amplidiag C. difficile+027 assays.
• Results were compared to reference laboratory strain collection data.

Main Results:

• Xpert assay misclassified five non-027 ribotypes (016, 019, 080, 176, and a variant of 046) as presumptive 027.
• Amplidiag assay misclassified two non-027 ribotypes (016, 176) as presumptive 027.
• Misclassified strains represented 1.6% of the reference laboratory strain collection.

Conclusions:

• Confirms the existence of non-027 C. diff strains closely related to hypervirulent 027 clones.
• These outliers can be misclassified by commercial molecular assays.
• Identified additional ribotypes (016, v046, 080) that can be misclassified, expanding the list of known outliers.