Jul 1, 1948

The rate of bactericidal action of penicillin in vitro as a function of its concentration, and its paradoxically reduced activity at high concentrations against certain organisms

The Journal of Experimental Medicine
H EAGLE, A D MUSSELMAN

Abstract

1. The concentrations of penicillin G which (a) reduced the net rate of multiplication, (b) exerted a net bactericidal effect, and (c) killed the organisms at a maximal rate, have been defined for a total of 41 strains of alpha- and beta-hemolytic streptococci, Staphylococcus aureus and Staphylococcus albus, Diplococcus pneumoniae, and the Reiter treponoma. 2. The concentration which killed the organisms at a maximal rate was 2 to 20 times the minimal effective level ("sensitivity" as ordinarily defined). With some organisms, even a 32,000-fold increase beyond this maximally effective level did not further increase the rate of its bactericidal effect. However, with approximately half the strains here studied (all 4 strains of group B beta-hemolytic streptococci, 4 of 5 group C strains, 5 of 7 strains of Streptococcus fecalis, 2 of 4 other alpha-hemolytic streptococci, and 4 of 9 strains of staphylococci), when the concentration of penicillin was increased beyond that optimal level, the rate at which the organisms died was paradoxically reduced rather than increased, so that the maximal effect was obtained only within a relatively narrow optimal zone. 3. There were marked differences between bacterial species, and occasionally b...Continue Reading

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Citations

Mentioned in this Paper

Exertion
Hypokinesia
Streptococcus agalactiae
Reiter Syndrome
Staphylococcus aureus
Enterococcus faecalis
Staphylococcus epidermidis
Penicillins
Allergy Testing Penicillin G
Streptococcus pneumoniae

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