Abstract
Summary
1. Reduction of the percentage of oxygen in the superambient air of broth cultures of the Type I pneumococcus greatly reduced or prevented bacteriostasis by sulfanilamide.
2. When the oxygen concentration was reduced to 0.04% an actual stimulus of growth by sulfanilamide was found.
3. When the oxygen was further reduced by the presence of pyrogallate or hydrosulfite the inhibition by sulfanilamide reappeared.
4. Hydrogen peroxide was detected only in cultures in equilibrium with atmospheres containing 10% oxygen or more. These concentrations correspond to those permitting effective bacteriostasis and are comparable to those obtainable in the plasma.
5. The lack of inhibition at intermediate concentrations shows that oxygen plays a vital rôle in the action of sulfanilamide. The failure to form peroxide at these same concentrations is taken as evidence that oxygen exerts its influence through the agency of hydrogen peroxide. The stimulus and recurring inhibition at the lowest values is interpreted as evidence of the formation of a toxic reduction compound, possibly a sulfide. The latter type of inhibibition may play a rôle in any bacteriostatic effect against anaerobes.
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