Association of NetF-positive type A Clostridium perfringens with necrotizing enteritis in neonatal foals
Bibliographic record
Abstract
A role for type A Clostridium perfringens in necrotizing enterocolitis of neonatal foals has long been suspected but incompletely characterized.The supernatant of an isolate made from a foal that died from this disease was highly cytotoxic for an equine ovarian (EO) cell line.Partial genome sequencing of an isolate revealed three novel putative toxin genes encoding proteins related to the pore-forming Leukocidin/Hemolysin Superfamily; these were designated netE, netF, and netG.netE and netF were located on one large conjugative plasmid, and netG was located with a cpe enterotoxin gene on a second large conjugative plasmid.Mutation and complementation showed that only netF was associated with the cytotoxicity.There was a highly significant association (p<0.0002) between the presence of netF with type A strains isolated from cases of foal necrotizing enterocolitis.netE and netF were found in all cytotoxic isolates, as was cpe, but netG was less consistently present.Pulsed-field gel electrophoresis showed that netF-positive isolates belonged to a clonal lineage that included canine-origin netF strains; some canine and equine netF-positive isolates were genetically indistinguishable.Equine antisera to recombinant Net proteins showed that only antiserum to rNetF had high supernatant cytotoxin neutralizing activity.The genomes of two C. perfringens strains recovered from a case of foal necrotizing enteritis (JP55) and canine haemorrhagic gastroenteritis (JP838), respectively, were completely sequenced using Single Molecule, Real-Time (SMRT) technology-PacBio and Illumina Hiseq2000.The JP55 and JP838 genomes include a single 3.34 Mb and 3.53 Mb circular chromosome, respectively, and both genomes additionally consist of five circular plasmids.Comparison of these two C. perfringens chromosomes with three fully sequenced reference chromosome sequences identified regions (~69 kb) shared between the two isolates, including regions forming a mosaic of plasmid-integrated segments, suggesting that these elements were acquired early in a clonal lineage of netF-positive C. perfringens strains.In addition, plasmid annotation revealed that both netF-positive C. perfringens strains, JP55 and JP838, harbour three tcp-conjugative plasmids in common, including a NetF/NetE toxins-encoding plasmid, a CPE/CPB2 toxins-encoding plasmid and a putative bacteriocin-encoding plasmid.We also found that JP55 and JP838 strains share unique virulence genes on conserved pathogenicity loci on the large tcp-conjugative plasmids.The identification of this novel NetF necrotizing toxin is an important advance in understanding the virulence of type A C. perfringens in necrotizing enteritis of neonatal foals.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".