Protocol development for the use of matrix assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) for detection of clostridium difficile toxin A and B from stool samples
Bibliographic record
Abstract
Background: Clostridium difficile is an anaerobic, Gram-positive, spore-forming bacillus. C. difficile is important in the medical community because it is the most common cause of antibiotic-associated diarrhea and infections can lead to serious complications such as toxic megacolon and pseudomembranous colitis. Infection is mediated by toxins A and B, both of which are proteins that undergo processing within the target cell to yield a 63 kDa active domain.\n\nObjective: This study investigates the use of MALDI-TOF-MS to detect the active domains of C. difficile toxins A and B from stool samples to explore the possibility of using MALDI as a diagnositc tool for C. difficile infections.\n\nMethods: Known toxin and antigen positive and negative stool samples sent from Royal Inland Hospital were diluted 10-fold in deionized water or phosphate buffered saline (PBS) and vortexed to create a relatively homogeneous suspension. Samples were then centrifuged and the pellet removed. Proteins in the supernatant were precipitated with acetonitrile or ammonium sulfate and the solution was centrifuged again. The pellet was resuspended in deionized water or TA30 and spotted on a MALDI plate with a sinnapinic acid (SA), SDHB (a mixture of 2,5-dihydroxybenzoic acid (2,5-DHB) and 2-hydroxy-5-methoxybenzoic acid), or CHCA (α-Cyano-4-hydroxycinnamic acid) matrix co-crystalized.\n\nResults and Discussion: MALDI analysis showed no difference between samples diluted in deionized water and those diluted in PBS. Protein precipitation with acetonitrile produced higher quality spectra than protein precipitation with ammonium sulfate. Sample co-crystalization with a SA matrix provided higher quality spectra than sample co-crystalization with a SDHB or CHCA matrix. MALDI analysis showed no peaks in the 63 kDa range in any of the samples. Because stool is a complex combination of materials, MALDI mass spectra were expected to be complicated and show vast differences between samples. Surprisingly, all ten MALDI spectra acquired were relatively similar. Similar individual ion signals were seen between 20 and 60 kDa and above 70 kDa. No individual ion signals were seen in the 63 kDa range in any of the samples, regardless of their being toxin and antigen positive or negative. This suggests that there is an open mass window for unambiguous detection of the 63 kDa active domain.\n\nConclusion: We were unable to use MALDI to detect the 63 kDa active domains of C. difficile toxins A and B from crude stool protein extracts. Further studies would be required to ascertain the possibility of using this technological tool to detect C. difficile toxins as an alternative method of diagnosis to the tests currently available. Although inconclusive, this study is a starting point for the investigation of MALDI as a diagnostic tool in a clinical setting.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.005 | 0.006 |
| Meta-epidemiology (narrow) | 0.004 | 0.003 |
| Meta-epidemiology (broad) | 0.003 | 0.003 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.036 | 0.033 |
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".