Detection of Toxigenic Clostridium difficile: Comparison of the Cell Culture Neutralization, Xpert C. difficile, Xpert C. difficile/Epi, and Illumigene C. difficile Assays
Bibliographic record
Abstract
Clostridium difficile is the most important cause of nosocomial diarrhea. Several laboratory techniques are available to detect C. difficile toxins or the genes that encode them in fecal samples. We evaluated the Xpert C. difficile and Xpert C. difficile/Epi (Cepheid, CA) that detect the toxin B gene (tcdB) and tcdB, cdt, and a deletion in tcdC associated with the 027/NAP1/BI strain, respectively, by real-time PCR, and the Illumigene C. difficile (Meridian Bioscience, Inc.) that detects the toxin A gene (tcdA) by loop-mediated isothermal amplification in stool specimens. Toxigenic culture was used as the reference method for discrepant stool specimens. Two hundred prospective and fifty retrospective diarrheal stool specimens were tested simultaneously by the cell cytotoxin neutralization assay (CCNA) and the Xpert C. difficile, Xpert C. difficile/Epi, and Illumigene C. difficile assays. Of the 200 prospective stools tested, 10.5% (n = 23) were determined to be positive by CCNA, 17.5% (n = 35) were determined to be positive by Illumigene C. difficile, and 21.5% (n = 43) were determined to be positive by Xpert C. difficile and Xpert C. difficile/Epi. Of the 50 retrospective stools, previously determined to be positive by CCNA, 94% (n = 47) were determined to be positive by Illumigene C. difficile and 100% (n = 50) were determined to be positive by Xpert C. difficile and Xpert C. difficile/Epi. Of the 11 discrepant results (i.e., negative by Illumigene C. difficile but positive by Xpert C. difficile and Xpert C. difficile/Epi), all were determined to be positive by the toxigenic culture. A total of 21% of the isolates were presumptively identified by the Xpert C. difficile/Epi as the 027/NAP1/BI strain. The Xpert C. difficile and Xpert C. difficile/Epi assays were the most sensitive, rapid, and easy-to use assays for the detection of toxigenic C. difficile in stool specimens.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.007 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".