Presence of a Group II Intron in a Multiresistant <i>Serratia marcescens</i> Strain That Harbors Three Integrons and a Novel Gene Fusion
Bibliographic record
Abstract
We analyzed the role of integrons in the dissemination of antibiotic resistance in a recent multiresistant clinical isolate, Serratia marcescens SCH88050909 (SCH909). This isolate harbors three integrons, all on a 60-kb conjugative plasmid. By PCR, hybridization, and sequencing analyses, we found that integron 1 has the dfrA1 and ant(3")-Ia cassettes. The first cassette in integron 2 contains the ant(2")-Ia gene, separated from its attC site (59-base element) by a 1,971-bp insert containing a group II intron; this intron codes for a putative maturase-reverse transcriptase on the complementary strand and is the first such intron to be found associated with an integron. The attC site is followed by a novel aminoglycoside resistance gene, ant(3")-Ii-aac(6')-IId, which has been characterized for its bifunctional ANT(3")-I and AAC(6')-II activities. DNA sequence analysis of this fused cassette suggests that insertion and excision due to the integrase activity could have an important role in the evolution of aminoglycoside resistance genes. This gene is followed by an unknown open reading frame with a typical attC site and a partial cassette composed of the beginning of the bla(OXA-10) cassette interrupted by IS1. The sequence downstream of IS1 revealed that the bla(OXA-10) cassette is incomplete and that the 3' conserved segment of this integron is absent. Integron 3 is in a Tn1696-like transposon with the aac(3)-Ia cassette followed by three unknown cassettes and ant(3")-Ia. The presence of the group II intron and the relationship of group II introns in eubacteria with mobile elements suggest a possible role of this element in events such as cassette formation and/or plasmid evolution.
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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) | 0.000 | 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".