Stability of four carbapenem antibiotics in discs used for antimicrobial susceptibility testing
Bibliographic record
Abstract
ABSTRACT In low-to middle-income countries, microbiological laboratories often use disc diffusion for antimicrobial susceptibility testing (AST). Reliable AST of carbapenem antibiotics is crucial for treatment decisions and surveillance purposes. Transport and storage conditions of materials used for AST are critical and may be challenging in some settings, where temperature cannot always be controlled. This study aimed to test the stability of four carbapenems in discs for AST under unfavourable conditions, i . e ., at room temperature and 35°C for up to 72 hours. Imipenem, meropenem, ertapenem, and doripenem discs from three brands, Oxoid, Becton Dickinson, and HiMedia, containing 10 μg of antibiotic were included. Discs were exposed to six unfavourable conditions and the recommended storage-condition as control. Subsequently, disc diffusion testing following the EUCAST guidelines was performed with four well-defined strains of Escherichia coli with different susceptibility profiles to carbapenems. The inhibition zone diameters were measured after 16-18 hours of incubation at 35±2°C. All experiments were executed in triplicate. In parallel, the carbapenems’ degradation was observed using a spectrophotometric method. Our study revealed that carbapenem discs were generally stable for AST although the concentration of most carbapenem antibiotics in discs decreased over time. Overall, imipenem (Oxoid and Becton Dickinson) discs were the most stable. Meropenem discs were less stable when exposed to 35°C than at room temperature. Concentrations of carbapenems in HiMedia discs were higher than those in Oxoid and Becton Dickinson. For carbapenem AST using disc diffusion in a rural area, we recommend using imipenem discs from Oxoid or Becton Dickinson. GRAPHICAL ABSTRACT HIGHLIGHTS In remote areas, transportation conditions of AST discs may be challenging Discs with four carbapenems from three brands were tested using six conditions Carbapenem discs were generally stable for AST In unfavourable conditions, concentrations in the discs degraded over time Imipenem (Oxoid and Becton Dickinson) discs were the most stable
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".