Phenotypic and Molecular Detection of CTX-M-β-Lactamases Produced by <i>Escherichia coli</i> and <i>Klebsiella</i> spp
Bibliographic record
Abstract
Organisms producing CTX-M-beta-lactamases are emerging around the world as a source of resistance to oxyiminocephalosporins such as cefotaxime (CTX). However, the laboratory detection of these strains is not well defined. In this study, a molecular detection assay for the identification of CTX-M-beta-lactamase genes was developed and used to investigate the prevalence of these enzymes among clinical isolates of Escherichia coli and Klebsiella species in the Calgary Health Region during 2000 to 2002. In addition, National Committee for Clinical Laboratory Standards (NCCLS) recommendations were evaluated for the ability to detect isolates with CTX-M extended-spectrum beta-lactamases (ESBLs). The PCR assay consisted of four primer sets and demonstrated 100% specificity and sensitivity for detecting different groups of CTX-M-beta-lactamases in control strains producing well-characterized ESBLs. Using these primer sets, 175 clinical strains producing ESBLs were examined for the presence of CTX-M enzymes; 24 (14%) were positive for bla(CTX-M-1-like) genes, 95 (54%) were positive for bla(CTX-M-14-like) genes, and the remaining 56 (32%) were negative for bla(CTX-M) genes. Following the NCCLS recommendations for ESBL testing, all of the control and clinical strains were detected when screened with cefpodoxime and when both cefotaxime and ceftazidime with clavulanate were used as confirmation tests.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".