Vaborbactam increases meropenem susceptibility in <i>Pseudomonas aeruginosa</i> clinical isolates displaying MexXY and AmpC upregulation
Bibliographic record
Abstract
ABSTRACT To evaluate the resistance mechanisms among Pseudomonas aeruginosa clinical isolates exhibiting meropenem (MEM) MIC values higher than meropenem-vaborbactam (MEV). P. aeruginosa clinical isolates collected in US hospitals from 2014 to 2019 were susceptibility tested. Whole-genome and transcriptome sequencing were performed. Results were analyzed for strain typing, acquired β-lactamases, and mutations in chromosomal genes; gene expression was measured for known β-lactam resistance contributors. Results were compared to a control group of 10 P . aeruginosa isolates displaying MIC values at 8 mg/L for meropenem ± vaborbactam (MEM = MEV). Out of 88 isolates displaying MEM > MEV, 33 (37.5%) isolates had reproducibly lower MIC values for meropenem-vaborbactam compared to meropenem when retested. The expression of mexX , mexY , mexZ , and ampC was significantly greater among a higher percentage of the MEM > MEV isolates. Furthermore, the association of mexXY and ampC overexpression was detected in 17/33 MEM > MEV isolates and only 1/10 MEM = MEV isolate. In addition, the Pseudomonas -derived cephalosporinase amino acid substitution R79Q was detected among 33.3% of the isolates displaying MEM > MEV, and none of the isolates displayed MEM = MEV. Other resistance mechanisms were not observed or were equally observed in both groups. In rare cases, vaborbactam plays a role in lowering the meropenem MIC values in P. aeruginosa clinical isolates likely due to the inhibition of the AmpC gene that was overexpressed in the presence of upregulation of MexXY with or without alterations in the AmpC gene. IMPORTANCE Pseudomonas aeruginosa isolates are intrinsically resistant to multiple antimicrobial agents and meropenem is an important therapeutic option to treat infections caused by this organism. Meropenem-vaborbactam activity is similar to that of meropenem alone against P. aeruginosa isolates. Isolates belonging to this species that display lower meropenem-vaborbactam compared to meropenem are rare. We initiated this study to understand the resistance mechanisms that could lead to lower meropenem-vaborbactam MIC values when compared to meropenem alone. We documented that isolates displaying lower meropenem-vaborbactam exhibited overexpression of MexXY and AmpC. In addition, isolates displaying the R79Q PDC (AmpC) mutation were more likely to display lower meropenem-vaborbactam when compared to isolates displaying the same MIC values for these agents.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".