1828. Bedaquiline Resistance in Mycobacterium intracellulare Is Mediated by the Transcriptional Repressor MmpT5
Bibliographic record
Abstract
Abstract Background Bedaquiline (BDQ) is an FDA approved antibiotic with antimycobacterial activity. BDQ resistance has been observed in several Mycobacterium species. High-level resistance is due to mutations in ATP synthase. Low -level resistance is attributed to drug efflux. Previously, we suggested that the MmpSL5 efflux system mediates BDQ resistance in M. intracellulare. Here, we examine the role of MmpT5 in transcriptional regulation of mmpSL5 and BDQ resistance. Methods In this study, mmpSL5-mmpT5 genes were cloned from 2 pre-treatment (wild-type mmpT5) and 2 relapse (mutant mmpT5) isolates of M. intracellulare and transformed into M. smegmatis. BDQ MICs were determined as well as cell survival after 24 hours exposure to an inhibitory concentration (0.07 µg/mL) of BDQ. Transcription of the M. intracellulare mmpT5 and mmpSL5 promoters was monitored with luciferase reporter gene fusions in the presence of wild-type and mutant alleles of mmpT5. Single and multigene constructs were created using the MoClo system, and transformed into E. coli DH5α. Constructs containing the M. tuberculosis rv0678 gene, which mediates low-level BDQ resistance in M. tuberculosis, were also examined. Results The BDQ MIC for the M. smegmatis control strain, and all strains containing mmpSL5-mmpT5 constructs, was 0.007 µg/mL. Even so, strains containing mutant mmpT5 alleles showed enhanced survival after 24 hours exposure to 0.007 µg/mL BDQ. Bacterial colonies associated with mutant mmpT5 alleles exhibited altered morphology relative to wild-type strains. Transcription of mmpSL5 was repressed by wild-type mmpT5, but neither mutant mmpT5 nor rv0678 repressed transcription. The mmpT5 luciferase reporter was not active. Conclusion MmpT5 represses transcription of mmpSL5 whereas the operon is dysregulated by mmpT5 mutations. Although Rv0678 regulates mmpSL expression in M. tuberculosis, it cannot repress the M. intracellulare mmpSL5 genes. The mmpSL5-mmpT5 genes have no impact on the BDQ MIC for M. smegmatis, but constructs containing mutant mmpT5 alleles do enhance bacterial survival. The altered morphology of these colonies suggests that BDQ resistance is mediated by cell wall changes in combination with drug efflux. Disclosures All Authors: No reported Disclosures.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".