Hyperbaric oxygen therapy augments the photodynamic action of methylene blue against bacteria in vitro
Bibliographic record
Abstract
Photodynamic therapy (PDT) entails the combination of photosensitizer and light to generate cytotoxic molecules that derive from molecular oxygen (O<sub>2</sub>). The presence of sufficient O<sub>2</sub> within the target tissues is critical to the efficiency of PDT. This study investigates the use of hyperbaric oxygen therapy in combination with PDT (HOTPDT) to augment the photodynamic action of methylene blue (MB) or 5-aminolevulinic acid (ALA) against gram positive and gram negative bacterial strains <i>in vitro</i>. <i>Staphylococcus aureus </i>or <i>Pseudomonas aeruginosa </i>were grown in trypticase soy broth as planktonic cultures (~10<sup>8</sup>/mL) or as established biofilms in 48 well plates (3 days old) at 32°C. Dark toxicity and PDT response in the presence or absence of HOT (2 atmospheres, 100% O<sub>2</sub> for 30, 60 or 120 min) was established for both MB (0-0.1 mM) and ALA (0- 1 mM) for a range of incubation times. The number of surviving colonies (CFU/mL) was plotted for each treatment groups. Light treatments (5, 10, 20 or 30 J/cm<sup>2</sup>) were conducted using an array of halogen bulbs with a red filter providing 90% transmittance over 600-800 nm at 21 mW/cm<sup>2</sup>. HOT increased the dark toxicity of MB (30 min, 0.1 mM) from < 0.2 log cell kill to 0.5 log cell kill. Dark toxicity of ALA (4 hr, 1 mM) was negligible and did not increase with HOT. For non-dark toxic concentrations of MB or ALA, (0.05 mM and 1 mM respectively) HOT-PDT enhanced the antimicrobial effect of MB against <i>Staphylococcus aureus</i> in culture by >1 and >2 logs of cell kill (CFU/mL) at 5 and 10 J/cm<sup>2</sup> light dose respectively as compared to PDT alone. HOT-PDT also increased the anti-microbial effects of MB against <i>Staphylococcus aureus</i> biofilms compared to PDT, albeit less so (> 2 logs) following 10 J/cm<sup>2</sup> light dose. Anti-microbial effects of PDT using ALA were not significant for either strain with or without HOT. These data suggest that HOTPDT may be useful for improving the PDT treatment of bacterial 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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".