InVitro characterization of colistin resistance and transfer of neomycin resistance in Escherichia coli O149 strains
Bibliographic record
Abstract
Neomycin, an aminoglycoside, is use at farm level for Escherichia coli treatment of piglets postweaning diarrhea, with 40% of unsuccessfully treatment due to the antimicrobial resistance.To overcome this situation, veterinarians use colistin also call polymyxin E, but this antibiotic is not homologated in Canada, even if it seems to be effective against E.coli.The described resistance to polymyxin is associated to a modification of the LPS core and the lipid A regions in the bacteria.For Salmonella, those modifications are associated to the two components system PmrA-PmrB.This system is known in E.coli but not yet reported to be implicated in colistin resistance.The neomycin resistance is linked to enzymatic modifications associated to genes located on plasmids.This study has for objectives to investigate the acquisition of colistin resistance and study the transfer of neomycin resistance between E.coli strains and other enterobacteria.E.coli O149 strains isolated from clinical cases (2008 to 2011) were used and susceptibility testing of strains was performed by the disk diffusion method.E-test and a micro-dilution method were used to determine the minimal inhibitory concentration (MIC) of colistin and neomycin respectively.All tested strains had a MIC higher than 128 ppm for neomycin whereas MICs were between 0.064 to 0.128 ppm for colistin, indicating that all strains were resistance to neomycin but all susceptible to colistin.In these isolates, neomycin antimicrobial resistance genes aac(3)-IV, apkA1 and aphA2 have been detected using PCR.Conjugation experiments are presently being performed.Colistin natural mutants (n=22) were created through serial passages on LB agar with 25xMIC.Sequencing of the PmrA-PmrB region of these mutants was performed to identify mutations.Three PmrA and seven PmrB mutations were for the first time reported in E.coli O149.Others mutants are still under investigation for other possible resistance mechanism.
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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 | 0.000 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".