Comparative Evaluation of Luminex xTAG® Gastrointestinal Pathogen Panel and Direct-From-Stool Real-Time PCR for Detection of C. difficile Toxin tcdB in Stool Samples from a Pediatric Population.

Detection of Clostridioides difficile toxins in patients with gastroenteritis has increasingly been accomplished through the use of enteric multiplex syndromic panels. Comparisons of the performance of these panels to both direct-from-stool (DFS) and culture-enriched stools followed by polymerase chain reaction (PCR) methods in pediatric populations are limited. Here, we compare the performance of the Luminex xTAG® Gastrointestinal Pathogen Panel (GPP) to our DFS in-house real-time PCR (DFS RT-PCR) assay for the detection of C. difficile toxin gene, tcdB, using 2641 stool specimens collected from children enrolled in the Alberta Provincial Pediatric EnTeric Infection Team (APPETITE) study in Alberta, Canada. We used culture enrichment followed by in-house RT-PCR to resolve discordant results between the two assays. We found excellent agreement (k = 0.89) between the GPP and our DFS RT-PCR assay: the positive percent agreement between the two assays was 97%, and the negative percent agreement was 99%. GPP, a multi-analyte platform can easily be implemented into a routine diagnostic laboratory for detecting enteric pathogens including C. difficile.

Direct Clostridioides difficile ribotyping from stool using capillary electrophoresis.

Clostridioides difficile(C. difficile) genotyping is essential for surveillance of emerging strains, transmissions, and outbreak investigations, but culture is lengthy and may not be routinely performed, which necessitates culture-independent genotyping methods. We aimed to develop a direct from stool C. difficile PCR ribotyping algorithm using capillary electrophoresis. Ribotypes were generated directly from 66.8% of stools with 33.2% requiring broth enrichment. 16S and tcdB cycle thresholds (Ct) were significantly lower (P< 0.001) in directly ribotyped stools compared to enriched stools, and Ct correlated with direct ribotyping (area under the curve: 0.97 and 0.96, respectively). Direct and isolate ribotypes were 94.7% concordant. Mixed C. difficile ribotypes were presumptively identified in 14 (7.5%) samples with 12 (6.4%) mixtures confirmed. We have developed a rapid PCR ribotyping algorithm allowing for direct C. difficile genotyping from stool using capillary electrophoresis with occasional detection of mixed C. difficile populations in stool, which is a limitation of conventional isolate genotyping.