Lineage and Virulence of<i>Streptococcus suis</i>Serotype 2 Isolates from North America
Bibliographic record
Abstract
We performed multilocus sequence typing of 64 North American Streptococcus suis serotype 2 porcine isolates.Strains were sequence type (ST) 28 (51%), ST25 (44%), and ST1 (5%).We identifi ed nonrandom associations between STs and expression of the virulence markers suilysin (SLY), muramidase-relased protein (MRP), and extracellular factor (EF).Expression of pili encoded by the srtF and srtG pilus clusters was also nonrandomly associated with STs.ST1 strains were SLY+ EF+ MRP+ srtF pilus+ srtG pilus-.ST25 strains were SLY-EF-MRP-srtF pilus-srtG pilus+, and most ST28 strains were SLY-MRP+ EF-srtF pilus+ srtG pilus+.ST28 isolates proved essentially nonvirulent in a mouse infection model; ST25 strains showed moderate virulence and ST1 isolates were highly virulent.ST1 is responsible for a high proportion of S. suis disease in humans worldwide.Its presence in North America indicates that potential zoonotic S. suis outbreaks in this continent cannot be disregarded. S treptococcus suis causes meningitis and septicemiain pigs and is a zoonotic agent (1).In the Western hemisphere, human S. suis disease is infrequent and usually affects workers in the swine industry.However, S. suis is the most commonly reported cause of streptococcal meningitis in adults in Vietnam and the second in Thailand (2,3).Two outbreaks of human S. suis disease have occurred in People's Republic of China, affecting hundreds of persons and causing 39 deaths (4).Most cases of animal and human S. suis infection have been caused by serotype 2 strains (5).The percentage of S. suis serotype 2 strains recovered from diseased pigs and the number of cases of human disease is lower in North America than in other parts of the world (6,7).Multilocus sequence typing (MLST) has shown that S. suis serotype 2 strains can be divided into at least 16 sequence types (STs).Closely related STs are grouped in the so-called ST complexes.Although ST complexes 1, 27, and 87 dominate the S. suis population, most invasive isolates belong to the ST1 complex (8).For example, most strains isolated from human patients in Japan were ST1 (9), whereas those causing the human outbreaks in People's Republic of China were ST7, included in the ST1 complex (10,11).However, Takamatsu et al. showed that 80% of the isolates recovered from blood or cerebrospinal fl uid of humans in Thailand belonged to STs grouped in the ST27 complex (12).Most of the S. suis serotype 2 strains genotyped so far by MLST originated in Europe and Asia (8-12).Isolates from Canada and the United States have received less attention.In this study, we used MLST to genotype a relatively large collection of US and Canadian S. suis serotype 2 strains. Materials and Methods S. suis Field StrainsSixty-four strains of S. suis serotype 2 isolated from pigs with clinical disease in different and nonrelated farms in major swine production areas of Canada and the United States were used.For comparison purposes, 19 porcine and 1 human S. suis serotype 2 strains isolated in Japan and Lineage and Virulence of Streptococcus suis Serotype 2Isolates from North America
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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 | 0.000 |
| 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".