<i>Staphylococcus aureus</i>small colony variants (SCVs) and their role in disease
Bibliographic record
Abstract
Persistent or difficult-to-treat Staphylococcus aureus infections in animals and humans may be related to small colony variants (SCVs) that can hide inside host cells and modulate host defenses. S. aureus SCVs have gained much attention in human medicine but have been underestimated and overlooked in veterinary medicine. Recently, an SCV isolated from a dairy cow with a history of chronic mastitis was shown to possess similar phenotypic and transcriptomic properties to those of human SCVs. SCVs form small, colorless, non-hemolytic colonies after 48 h, are only slowly coagulase positive, fail to ferment mannitol, and can revert to the parental phenotype. The phenotype of SCVs is mostly related to alterations in hemin and/or menadione biosynthesis or to thymidine deficiency. Transcriptomic analysis of SCVs shows up-regulation of genes involved in glycolytic and arginine-deiminase pathways, capsular biosynthesis; increased sigma B activity; and down-regulation of genes for α-hemolysin, coagulase and effector molecule RNA III of the global virulence regulator Agr. Similar results are reported at the protein level. SCVs are less virulent but successful persisters in infection models. SCVs persist longer and at higher numbers within non-phagocytes than do their parents. SCVs survive within spacious vacuoles up to 24 h within cultured bovine mammary epithelial cells, likely due to up-regulation of protective mechanisms that counteract the lethal acidic environment of the phagolysosome. Persistence of SCVs within host cells may explain failures in antimicrobial therapy and vaccinations.
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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 | 0.001 | 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".