Relative virulence of Staphylococcus aureus bovine mastitis strains representing the main Canadian spa types and clonal complexes as determined using in vitro and in vivo mastitis models
Bibliographic record
Abstract
Staphylococcus aureus is one of the main pathogens leading to both clinical and subclinical bovine mastitis in dairy cattle. Prediction of disease evolution based on the characteristics of Staph. aureus isolates that cause intramammary infections and understanding the host-pathogen interactions may improve management of mastitis in dairy herds. For this study, several strains were selected from each of the 6 major Canadian spa types associated with mastitis (t267, t359, t529, t605, t2445, and t13401). Adherence to host cells and intracellular persistence of these strains were studied using a bovine mammary gland epithelial cell line (MAC-T). Additionally, relative virulence and host response (cytokines production) were also studied in vivo using a mouse model of mastitis. Whole-genome sequencing was performed on all strains and associations between clonal complex, sequence type, and presence of certain virulence factors were also investigated. Results show that spa type t2445 was correlated with persistence in MAC-T cells. Strains from spa t359 and t529 showed better ability to colonize mouse mammary glands. The exception was strain sa3154 (spa t529), which showed less colonization of glands compared with other t359 and t529 strains but possessed the highest number of superantigen genes including tst. All strains possessed hemolysins, but spa types t529 and t2445 showed the largest diameter of β-hemolysis on blood agar plates. Although several spa types possessed 2 or 3 serine-aspartate rich proteins (Sdr) believed to be involved in many pathogenic processes, most t529 strains expressed only an allelic variant of sdrE. The spa types t605 (positive for the biofilm associated protein gene; bap+) and t13401 (bap-), that produced the largest amounts of biofilm in vitro, were the least virulent in vivo. Finally, strains from spa type t529 (ST151) elicited a cytokine expression profile (TNF-α, IL-1β and IL-12) that suggests a potential for severe inflammation. This study suggests that determination of the spa type may help predict the severity of the disease and the ability of the immune system to eliminate intramammary infections caused by Staph. aureus.
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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".