The distribution, diversity and functional characterization of the Listeria Genomic Island 1
Bibliographic record
Abstract
Listeria monocytogenes was the causative agent of the nationwide 2008 outbreak associated with contaminated ready-to-eat meat products. Within the whole genome DNA sequences of the outbreak isolates we previously identified a novel 50kb genomic island, designated as Listeria Genomic Island 1 (LGI1). LGI1 is predicted to contribute to Listeria pathogenesis and/or environmental persistence because it encodes genes related to known virulence factors and mobilization functions, including a putative type IV secretion system and a putative small multidrug resistance efflux pump. The distribution of LGI1 in Canadian L. monocytogenes isolates was determined by PCR screening for LGI1 within 126 isolates from 1987 to 2010 that represented different serotypes and pulsed-field gel electrophoresis (PFGE) patterns. To assess the evolutionary history and genetic diversity of this island, total LGI1 sequences from 15 whole-genome sequences were compared, and from the full study panel of isolates,PCR screening for the chromosomal insertion site and multiple LGI coding sequences were performed. LGI1 was detected almost exclusively in serotype 1/2a isolates, and within those, the isolates predominantly had the same PFGE patterns. These LGI1-encoding isolates also exclusively belonged to the multi-locus sequence typing (MLST)clonal complex 8. LGI1 was highly genetically conserved and it was inserted at the same location within the genome in 65 of the 67 isolates that harboured the island. To study the function and expression of LGI1, antimicrobial susceptibility assays,bioinformatic analyses and real-time reverse-transcription PCR were used. Isolates encoding LGI1 had an increased tolerance to quaternary ammonium compounds commonly used in sanitizing agents (benzalkonium chloride (BCl) and benzethonium chloride (BeCl)) compared to isolates lacking LGI1 (but still highly related by MLST and PFGE). LGI1 is also tightly regulated, with expression of 13 of 16 tested coding sequences only being induced by the presence of sub-inhibitory concentrations of BCl,and one predicted regulator being expressed under all conditions. This study indicates that the vast majority LGI encoding CC8 isolates share a common progenitor L. monocytogenes ancestor that acquired LGI1 in a single evolutionary event. LGI1 has remained genetically conserved since that time, and the functions contributed by this island minimally include an increased tolerance to sanitizer agents.
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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 | 0.001 | 0.001 |
| 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".