The silver cation (Ag+): antistaphylococcal activity, mode of action and resistance studies
Bibliographic record
Abstract
OBJECTIVES: To examine several poorly understood or contentious aspects of the antibacterial activity of silver (Ag(+)), including its cidality, mode of action, the prevalence of resistance amongst clinical staphylococcal isolates and the propensity for Staphylococcus aureus to develop Ag(+) resistance. METHODS: The effects of Ag(+) on the viability, macromolecular synthesis and membrane integrity of S. aureus SH1000 were assessed using established methodology. Silver nitrate MICs were determined for a collection of staphylococcal isolates (n = 1006) collected from hospitals across Europe and Canada between 1997 and 2010. S. aureus biofilms were grown using the Calgary Biofilm Device. To examine the in vitro development of staphylococcal resistance to Ag(+), bacteria were subjected to continuous subculture in the presence of sub-MIC concentrations of Ag(+). RESULTS: Silver was bactericidal against S. aureus in buffered solution, but bacteriostatic in growth medium, and was unable to eradicate staphylococcal biofilms in vitro. Challenge of S. aureus with Ag(+) caused rapid loss of membrane integrity and inhibition of the major macromolecular synthetic pathways. All clinical staphylococcal isolates were susceptible to ≤ 16 mg/L silver nitrate and prolonged exposure (42 days) to Ag(+) in vitro failed to select resistant mutants. CONCLUSIONS: The rapid and extensive loss of membrane integrity observed upon challenge with Ag(+) suggests that the antibacterial activity results directly from damage to the bacterial membrane. The universal susceptibility of staphylococci to Ag(+), and failure to select for resistance to Ag(+), suggest that silver compounds remain a viable option for the prevention and treatment of topical staphylococcal infections.
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How this classification was reachedexpand
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 | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".