A Paradoxical Zone Phenomenon in the Bactericidal Action of Penicillin in Vitro
- 9 January 1948
- journal article
- research article
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 107 (2767) , 44-45
- https://doi.org/10.1126/science.107.2767.44
Abstract
Five of 7 strains of Streptococcus faecalis treated with penicillin were rapidly killed at a conc. of 4 [gamma]/ml., at which 99.9% of the organisms were rendered nonviable in 5-7 hrs. All 5 were killed much more slowly at higher concs. of penicillin. Three of 4 other strains of a-hemolytic streptococci showed a similar zone phenomenon. Of 13 strains of [beta]-hemolytic streptococci (Lancefield groups A, B, C), 5 group A strains did not show the zone phenomenon. However, all 4 of the group [beta] strains and 2 of 4 group C strains showed zonal susceptibility. Three of 7 strains of Staphylococcus aureus and 1 of 2 strains of S. albus showed the phenomenon. The phenomenon was found to be related to the number of organisms inoculated. The larger the inoculum, the more pronounced was the difference in the rate at which the organisms were killed at high and low concs. of penicillin.Keywords
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