Abstract
Conclusions
In the absence of organic matter, iodine killed Staphylococcus aureus in a dilution of 1:20,000 and Eberthella typhosa in a dilution of 1: 17,500 in 10 minutes at 37°C. In the presence of organic matter the dilutions were reduced to 1:2000 for Staph. aureus and 1: 1750 for E. typhosa. Iodine dissolved in a 1:3000 dilution of an oxidation-reduction solution (Composed of a mixture of one mole each of manganous sulfate and ferric sulfate) killed Staph. aureus in a dilution of 1:80,000 and E. typhosa in a dilution of 1:60,000, both in the absence of organic matter. In the presence of organic matter the killing dilutions were 1:5000 and 1:4500 respectively.
A dilution of 1:2000 of the o-r solution killed embryonic chick heart tissue fragments in 10 minutes at 37°C. Iodine dissolved in a 1:3000 o-r solution killed the tissue fragments in a dilution of 1:3750 of iodine.
Toxicity indexes may be calculated by dividing the highest dilution of iodine required to kill the tissue by the highest dilution required to kill the test organism under the same conditions. The Toxicity Index of iodine + 1:3000 o-r solution was 0.05 for Staph. aureus and 0.06 for E. typhosa. The Toxicity Index of iodine alone was 0.2 for Staph. aureus and 0.23 for E. typhosa. Theoretically, an index less than one means that the germicide is more toxic to bacteria than to tissue; an index greater than one means that the germicide is more toxic to tissue than to bacteria. The smaller the index the more nearly perfect the germicide.
When iodine was dissolved in a 1:3000 o-r solution composed of manganous and ferric chlorides instead of the sulfates, the Toxicity Indexes were 0.042 for Staph. aureus and 0.1 for E. typhosa.
The importance of this observation is discussed.
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