Role for RTX-family toxin HlyA of extraintestinal pathogenic <i>Escherichia coli</i> in serum resistance
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Abstract Extraintestinal pathogenic Escherichia coli (ExPEC) is a major cause of urinary tract infections, bacteraemia, and sepsis. CFT073 is a prototypic, urosepsis isolate of sequence type (ST) 73. ST73 isolates are associated with higher virulence scores than other pandemic clonal groups, such as ST131. This laboratory, among others, has previously shown that strain CFT073 is serum-resistant, with virulence factors such as the exopolysaccharide capsule and other extracellular polysaccharides imparting resistance to the complement system. In this study, it was shown that culture supernatants were protective in standardized serum killing assays, when compared to cultures standardized in fresh medium. Diluting cultures in fresh medium in place of conditioned medium significantly increased sensitivity of CFT073 to serum, indicating that a secreted factor may provide resistance to serum. Haemolysin, a pore-forming toxin, is secreted by CFT073 in a calcium-dependent manner. This study found that a CFT073 hlyA mutant is significantly more sensitive to 50% serum than the wild-type, implicating haemolysin in the response of CFT073 to serum. In addition to acting as a toxin upon secretion, it has been shown previously that HlyA forms a complex with lipopolysaccharide (LPS), which permits modulation of host immune responses by HlyA whilst cell-associated. The effect of HlyA on capsule expression and serum resistance was examined and characterized in this study, with results indicating that perhaps the HlyA–LPS complex interacts with surface capsule. This study is the first to identify haemolysin as a virulence factor promoting resistance to serum in CFT073, acting whilst associated with the cell.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 it