Adamantane Resistance in Seasonal Human Influenza A Viruses from Calgary, Alberta (January 2007 to August 2008)
Bibliographic record
Abstract
The available antivirals for the treatment and prophylaxis of influenza A infections include the adamantanes (amantadine and rimantadine), which are matrix (M2) protein inhibitors, and the neuraminidase inhibitors (oseltamivir and zanamivir). Resistance to the adamantanes is conferred by mutations at amino acid positions 26, 27, 30, 31 or 34 within the M2 protein of influenza A viruses. A significant increase in adamantane resistance has been reported worldwide since 2003, reflected by a similar increase in Canada. The present study reports on the frequency of adamantane resistance in seasonal influenza A viruses in Calgary, Alberta, for the period between January 2007 and August 2008, as an update to the previous report. Positive influenza A samples (221 original patient specimens and 34 isolates obtained by viral culture) were analyzed for changes in the critical amino acid residues of the M2 gene. The amplification and sequencing of regions that confer adamantane resistance directly from RNA extracts of clinical samples (without previous culture) makes this approach a fast and efficient process for monitoring resistance. The results showed that the frequency of resistance varied from 37.5% to 49.2% in circulating influenza A H3N2 virus strains (n=213) between January 2007 and April 2007. The frequency of resistance increased to 100% in May 2007, after which all H3N2 viruses were resistant until the end of the monitoring period. All resistant H3N2 viruses contained the serine to asparagine substitution at amino acid position 31. Resistance was not observed in the H1N1 viruses tested (n=39) within this monitoring period. The level of adamantane resistance in H3N2 viruses continues to remain high since resistant viruses became the prevalent circulating strains in 2005. Recent reports have indicated that the currently circulating swine-origin influenza A H1N1 subtype viruses are adamantane resistant. It is, thus, important to continue to monitor seasonal influenza A viruses for antiviral resistance markers to ensure optimal prophylaxis and treatment.
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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 | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".