Examining biofilm formation and copper susceptibility testing methods in Pseudomonas aeruginosa sink drain isolates to study the role of the GI-7 genomic island
Bibliographic record
Abstract
Copper is an antimicrobial metal used in sink drains that is becoming ineffective due to copper tolerance of species such as Pseudomonas aeruginosa enhanced by the presence of the genomic island GI-7. Studies of copper tolerance associated with GI-7 are hindered by the lack of accurate planktonic and biofilm testing methods to determine copper susceptibility, and a lack of knowledge regarding the prevalence of this sequence amongst Canadian Pseudomonas isolates. In chapter 3, we developed a new deep well biofilm device that provided increased surface area for biofilm biomass formation. This method can be used to screen antimicrobial susceptibility in a 96-well high throughput format. The increased surface area allowed for greater biofilm biomass per mm2 as compared to the standard device and revealed plastic preferences in biofilm biomass formation by P. aeruginosa and Escherichia coli. Both devices produced different minimum biofilm eradication (MBEC) values for benzalkonium chloride and bleach, yet both were suitable for biofilm cultivation. In chapter 4, we examined 2467 genome sequenced Pseudomonas isolates collected from a 2017-2019 Ontario hospital intensive care unit study. Isolates from patients and hospital rooms with regular and copper sink drains were collected and used to explore if GI-7 presence was associated with copper sink drains. This analysis revealed that GI-7 is widely spread across clinical and environmental isolates of certain multi-locus sequence types, but statistical analyses did not show significant associations between GI-7 and copper sink drains due limited sampling from copper sink drains. Some correlation trends amongst GI-7 isolates were noted and discussed. Finally, phenotypic characterization of P. aeruginosa GI-7 copper tolerance through planktonic and biofilm culturing methods was examined with various P. aeruginosa strains. Copper salt addition to media caused lethal acidification that inhibited both planktonic and biofilm culture growth, regardless of GI-7 presence. To overcome this, we modified a previously used copper water exposure method to eliminate the effects of copper acidity and verify copper tolerance differences between susceptible PAO1 and PA-8 strains with and without GI-7. Overall, our findings offer improved techniques for studying copper tolerance and exploring the role of GI-7 in Canadian hospital Pseudomonas isolates.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".