Evaluation of the NG-Test® CTX-M MULTI lateral flow immunoassay and genomic discovery of a blaCTX-M-27 variant with a premature stop codon
Bibliographic record
Abstract
Timely identification of extended-spectrum beta-lactamase (ESBL)-producing bacteria supports early antimicrobial optimization, especially for patients with invasive infections. NG-Test® CTX-M MULTI (CTX-M LFA) is a rapid immunochromatographic assay for detection of Cefotaximase-Munich (CTX-M)-type ESBL. We evaluated its performance against existing molecular platforms. A sampling of archived Gram-negative bacteria (including Enterobacterales and non-fermenters) was included in the study. All isolates underwent testing for CTX-M ESBL by CTX-M LFA. CTX-M LFA results were compared to results from molecular methods, laboratory-developed (LD)-PCR (2013-2019) or BCID2 (2022-2023). Discordances were resolved with a combination of ESBL phenotypic testing and an alternative PCR platform, or whole-genome sequencing. Seventy-eight isolates were included in the study, all of which underwent CTX-M LFA and molecular testing ( n = 47 by LD-PCR, n = 31 by BCID2). Post-discordance analysis showed positive percent agreement of 89.7 % (95 %CI 71.5-97.2 %), negative percent agreement 100 % (95 %CI 90.9-100 %) and overall categorical agreement 96.2 %, κ=0.92 (95 %CI 88.4-99.0 %). One E. coli was negative by CTX-M LFA but positive for bla CTX-M by BCID2. Whole-genome sequencing identified a non-functional bla CTX-M-27 gene with adenine insertion at position 70 in codon 24, causing a frameshift mutation resulting in a premature stop codon (codon 58). CTX-M LFA improved performance in comparison with molecular methods by accurately identifying an isolate with a prematurely truncated protein as a true-negative for CTX-M. This highlights potential limitations of molecular-based resistance detection. CTX-M LFA was simple to perform and yielded results within 15 minutes.
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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 | 0.004 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.001 | 0.001 |
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".