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.

摘要: 1. The concentrations of penicillin G which ( a ) reduced the net rate multiplication, b exerted bactericidal effect, and c killed organisms at maximal rate, have been defined for total 41 strains α- s-hemolytic streptococci, Staphylococcus aureus albus, Diplococcus pneumoniae , Reiter treponoma. 2. concentration was 2 to 20 times minimal effective level ("sensitivity" as ordinarily defined). With some organisms, even 32,000-fold increase beyond this maximally did not further its effect. However, with approximately half here studied (all 4 group B 5 C strains, 7 Streptococcus fecalis other α-hemolytic 9 staphylococci), when increased that optimal level, died paradoxically rather than increased, so effect obtained only within relatively narrow zone. 3. There were marked differences between bacterial species, occasionally different same respect penicillin, but also they could be by drug in any concentration. Although there rough correlation these two factors, many exceptions; individual affected high might nevertheless rapidly, while sensitive minute slowly. 4. Within suspension, varied minor degree penicillin. They strikingly, however, their resistance measured required kill varying proportions cells.