A phenotypic and molecular comparison of community-associated and hospital-associated methicillin-resistant Staphylococcus aureus in Canada
Bibliographic record
Abstract
Methicillin resistan| staphylococcus an¿reus (MRSA) was first described in 1961 only one year after methicillin was introduced clinically.MRSA was initially restricted to the healthcare settings, but recently has become prevalent in the community setting.community-associated MRSA (CA-MRSA) is generally sensitive to most non-B-lactam a¡timicrobials and commonly causes skin and soft tissue infections however, GA-MRSA has been linked to severe infections such as necrotizing pneumonia.CA-MRSA strains typically contain Staphylococcal cassefte chromosome n¡e c (sccmec) type rv and the Panton-Valentine leukocidin (PVL) toxin.One hundred sixteen methicillin-sensitive S. aarzzs (MSSA) and 26 MRSA were collected fiom east-central saskatchewan as part ofan on-going case control sfudy.Previously characterized MRSA ÍÌom the region were also included in antimicrobial resistance investigations.Newly collected strains were characterized by antimicrobial susceptibility testing, DNA fingerprinting using pulse-field gel electrophoresis (pFGE) and PCR to detect the genes responsible for PVL.pcR was used to detect eryth¡omycin resistance genes and a D-test was used to confirm inducible clindamycin resistance in all erythromycin resistant strains.PCR was also used to detect the pre sence of the mupA mupirocin resistant gene.MSSA strains possessed a low level of antimicrobial resistance overall with 52% of strains sensitive to all antimicrobials tested.However, erythromycin resistance was of notable levels.Among the erythromycin resistant MSSA, pcR results revealed an even distributton of ermA, erntc and ntsrA resistance determinants, which is reflective of the large amount of diversity of pFGE pattems.Two MSSA strains were determined to be PVL positive, which is not unexpected, as pv]is known to exist in a small number of MSSA.kr both the new and previously characterized MRSA from the region, erythromycin resistance was hìgh being present in 53% ofstrains.Ofthe erythromycin resistant MRSA, 61% were constitutively or induciblely clindamycin resistant due to the presence of ennC, The remaining erythromycin resistant strains contained msrA and were sensitive to clindamycin.When erythromycin resistance in MRSA from Saskatchewan was compared to that of MRSA strains collected from Canadian Nosocomial Infection Surveillance (CNISP) sites, the level of erythromycin resistance was found to be lower in strains fiom Saskatchewan.Among the CMRSA2 from Saskatchewan ermC, was the most prevalent resistance gene while in CMRSA2 from CNISP sifes ermA, was the most prevalent.CMRSAT from CNISp sites was found to have a lower amount of erythromycin resistance as well as a lower amount of inducible clindamycin resistance.A high r ate (55%) of mupirocin resistance was observed in all MRSA from the region.Mupirocin resistance in MRSA was found to be due to rnupA, which was shown to be carried on at least two distinct plasmids through plasmid restriction analysis and Southem blotting.During routine investigation of PVL in CA-MRSA from CNISp sites, pVL was found to be absent in 31 of 76 CA-MRSA strains that had indistinguishable pFGE pattems.The strains were Canadian PFGE type 0142, which is indistinguishable from MW2ruSA400 CA-MRSA strain.It was found that a homologous phage that does not contain PVL was inserted into the same site.There does not appear to be a difference in the number ofinfections versus colonizations or in the types ofinfections among the pvlpositive and PVL negative strains suggesting that PVL may not be as important in milder infections as previously thought.vi, List of Abbreviations Ala Alanine ATP Adenine Tri-Phosphate bp
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".