Diversity among verotoxin-producing Escherichia coli 0103:H42
Bibliographic record
Abstract
The objectives of the research were to identify and characterize VTEC in the feces of Ontario beef cattle and to characterize in detail strains of a selected non-O157 VTEC serotype. Cultures of rectal feces from 500 cattle were screened for verotoxin (VT) by ELISA and PCR for genes for verotoxins ('vt1' and 'vt2') and intimin ('eae'). A VT-immunoblot was used to isolate VTEC from VT-ELISA-positive samples. Prevalence rates of VTEC by VT-ELISA and PCR were 10.2 % and 6.2 %, respectively. VTEC isolated from 27 of 51 VT-ELISA-positive samples belonged to 24 serotypes, five (20.8%) had 'vt1 'only, 19 (79.2%) had 'vt2' either alone (3) or in various combinations with 'vt1, vt2c, vt2d; ' and two (8.3%) were 'eae'-positive. The distribution of selected putative virulence genes was: 'ehxA', 62.5%; ' espP', 45.8%; 'saa', 66.6%; 'subA', 54.1%. Nine isolates were resistant to antimicrobials. VTEC of serotype O103:H2 of bovine and human and of North American and European origins were selected for detailed characterization. Ninety-three O103:H2 VTEC strains were characterized by virulence genes, pulsed-field gel electrophoresis (PFGE), plasmid profiling, phenotype, antimicrobial resistance and VT production. All strains were positive for 'vt1 'and 'eae 'and 94.6% posessed 'ehxA'. Two strains carried 'vt2'. PFGE differentiated 68 profiles grouped in six clusters and there were 25 plasmid profiles. The proportions of strains with 'katP 'and ' etp 'genes were significantly higher in European compared to North American human strains. All strains carried genes 'Z4326, Z4332' and 'Z4333 'and 32.2% carried 'Z4321'. Genes ' terC, iha' and 'ureC 'were present in 66.6%, 44.08% and 67.7% of strains, respectively. The distribution of selected phenotypes was: EHEC-hemolysin, 95%; alpha hemolysin, 2%; tellurite resistance, 67%; urease, 1.%; colicin production, 38%; antimicrobial resistance, 57%. VT1 concentrations were significantly increased in low iron cultures. Phages were induced by UV irradiation but not by mitomycin. Thirty-two VT1-phages and two VT2-phages were isolated from 33 strains and belonged to 22 RFLP phage subtypes. All phages carried the 'Q 'and 'P 'genes and 21/34 produced an amplicon for the Q-stx'A1' region. The proportion of human strains that yielded phages (22/48) was significantly higher than that of cattle strains (10/45) (p = 0.02).
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".