ANTIMICROBIAL RESISTANCE AND GENOMIC CHARACTERIZATION OF NORTH AMERICAN MELISSOCOCCUS PLUTONIUS ISOLATES
Bibliographic record
Abstract
European foulbrood (EFB) is a disease of honey bee larvae caused by Melissococcus plutonius. Western Canada has seen a recent emergence of EFB disease despite oxytetracycline (OTC) use, resulting in economic losses for beekeepers. In North America, antimicrobials are widely used for treatment and control of bacterial brood diseases, including both American foulbrood (AFB) and European foulbrood (EFB) disease. In contrast, prophylactic antimicrobial-use is prohibited in beekeeping in the European Union. Thus, antimicrobial resistance (AMR) poses an imminent threat to North American apiaries, especially for cases of EFB disease since only a single antibiotic, oxytetracycline (OTC), is approved for use. In contrast, tylosin (TYL) and lincomycin (LMC) are also registered for use against AFB. The most recently published antibiotic sensitivity testing for M. plutonius was performed approximately 20 years ago on M. plutonius isolates from outside North America. Moreover, little is known about the resistance profiles of M. plutonius and how these are related to the efficacy and ability of drugs to clear infection in honey bee larvae. To address these issues, we sought to investigate OTC, TYL, and LMC as potential treatment options for EFB disease using laboratory-reared larvae infected with M. plutonius. Moreover, our study aims to determine if antibiotic resistance to OTC TYL, or LMC exists in North American M. plutonius isolates. Genomic characterization of Canadian isolates is lacking as well, and thus we also aimed to characterize a subset of isolates we did antimicrobial susceptibility testing for. Firstly, the utility of OTC, TYL, and LMC were compared through an experimental design that either mimicked Metaphylaxis or antimicrobial intervention, using concentrations that corresponded to previous studies. We found that all concentrations prevented clinical signs of EFB disease following infection with M. plutonius 2019BC1 in vitro. Interestingly, M. plutonius 2019BC1, following antimicrobial susceptibility testing was characterized as resistant to OTC, with a minimum inhibitory concentration (MIC) of 32 µg/mL. Accordingly, we then compared the utility of the three drugs using four M. plutonius isolates that demonstrated a range of resistance phenotypes. Additionally, treatment doses were determined through corresponding MICs. We demonstrate that infections and the efficacy of antimicrobial treatments in honey bee larva are concordant with in vitro MIC measurements and that the survival outcomes of larva are not dependent on M. plutonius clearance but a strain-dependent reduction of their numbers within larva. To assess the range of antimicrobial resistance present in North America, a total of 67 M. plutonius isolates. We found that a majority of isolates had a minimum inhibitory concentration that indicated resistance to OTC (> 16 μg/mL), while all isolates had MICs that corresponded to sensitivity against tylosin and lincomycin (< 4 μg/mL). Interestingly, resistant isolates showed sensitivity to OTC when different media was used, indicating that resistance is media-dependent. 53 of these isolates were used for whole genome sequencing and genomic comparison with 17 publicly available M. plutonius genomes. Through genomic characterization, we did not identify a resistance gene to explain the resistance seen for OTC. Moreover, phylogenetic analysis demonstrated that OTC resistance was not clustered together. However, similar clonal complexes cluster together.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".