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Quantitative cidal activity of hyperbaric oxygen for opportunistic yeast pathogens
Aviation, Space, and Environmental Medicine
|October 1, 1978
Summary
Hyperbaric oxygen (O2) demonstrates significant cidal activity against human-derived yeasts, with 81% exhibiting total kill. Carbon dioxide (CO2) presence slightly modulates this effect, highlighting differences between eukaryotic and prokaryotic cells.
Area of Science:
- Microbiology
- Hyperbaric Medicine
- Cell Biology
Background:
- Yeasts, particularly Candida species, are common human pathogens.
- Hyperbaric oxygen therapy involves exposure to increased oxygen partial pressures.
- Understanding the antimicrobial effects of hyperbaric oxygen is crucial for clinical applications.
Purpose of the Study:
- To evaluate the cidal activity of hyperbaric oxygen (O2) and O2 with carbon dioxide (CO2) against various human-pathogenic yeasts.
- To investigate the influence of different oxygen and CO2 concentrations and pressures on yeast viability.
- To compare the response of yeasts to hyperbaric conditions with that of bacteria.
Main Methods:
- Assaying the cidal activities of 24-hour exposures to 100% O2 and 95% O2 + 5% CO2 at 1 and 3 atmospheres absolute (ATA).
- Testing 21 yeast strains, including multiple species of Candida and Torulopsis, isolated from human sources.
- Quantifying yeast kill rates under different hyperbaric conditions.
Main Results:
- 17 out of 21 (81%) yeast strains showed high sensitivity to hyperbaric oxygen, with kill indices ranging from 80-100%.
- Hyperoxia alone at 1 ATA was not lethal.
- CO2 deprivation enhanced cidal activity in only 2 strains, while the O2+CO2 mixture enhanced it in 4 strains, with no significant difference for the remaining 15.
Conclusions:
- Hyperbaric oxygen exhibits potent cidal activity against a majority of human-derived yeasts, with notable species and strain variations.
- The role of CO2 in modulating hyperbaric oxygen's cidal effect on yeasts differs from its effect on bacteria.
- These findings underscore fundamental differences in the response of eukaryotic (yeast) and prokaryotic (bacterial) cells to hyperbaric oxygen and CO2 deprivation.