301. The Use of Multiplex Touchdown PCR to Genotype <i>Cutibacterium</i> (<i>Propionibacterium</i>) <i>acnes</i> Isolated from Periprosthetic Shoulder Infections
Bibliographic record
Abstract
As biogeographic surveys of the human skin microbiome have shown that C. acnes is a major component of the residential axillary microflora, the organism is frequently isolated from synovial tissue and joint aspirates obtained from patients with suspected periprosthetic shoulder infections. We hypothesized that multilocus sequence typing (MLST) applying a prior validated rapid high through-put multiplex PCR protocol would segregate C. acnes into distinctive phylogroups associated with periprosthetic infections compared with commensal strains. C. acnes collected between 2015 and 2017 were correlated with the presence or absence of infection in a detailed retrospective chart review. To determine the C. acnes genotype, bacterial genomic DNA isolated from a single patient isolate served as template in a six locus multiplex touchdown PCR assay using organism-specific primers targeting six genes (16S rRNA, ATPase, sodA, Fic toxin, aspD and recA). Isolates were classified as a contaminant in the absence of multiple positive cultures from an anatomic site and without corresponding clinical, laboratory and histopathologic correlates of infection. The assignment of a diagnosis of prosthetic joint infection (PJI) conformed to the definition recommended by the IDSA Clinical Practice Guidelines of PJI. Of the C. acnes recovered from 94 patients, 14 (14.9%) were from patients with shoulder implants of which shoulder PJI was present in 10 individuals (10.6% of the total). The remaining 84 (89.4%) isolates were retrieved from a variety of tissue and fluid samples of which the majority (65.5%) were deemed as contaminants. Overall, phylogroups IA1, IB, and II predominated (79.8%). Although a similar genetic profile was present in all of the shoulder isolates, no phylogroup association was detected with PJI (P < 0.72). No genetic difference was present in the lineage of strains not causing PJI compared with those responsible for PJI (P < 0.25). Our results mirror those from a previous investigation using a less robust four gene MLST PCR based scheme that showed a lack of a phylogenetic association with shoulder PJI. Our results are a reflection of the phylogroup composition of the circulating C. acnes sequence types in our community. All authors: No reported disclosures.
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".