Action of Penicillin onStaphylococcus

Abstract

A 4-hr. culture of S. aureus was exposed to penicillin at 37[degree] C. At intervals, samples were taken for counts of viable bacteria. At low penicillin concns. the lethal effect of this antibiotic agent on Staphylococcus is preceded by a period of unaffected growth. At higher concs, the lethal action appears to begin without lag. When Staphylococcus is exposed to penicillin at 37[degree] C for a time, and the cells then removed to a penicillin-free medium, the effect of penicillin persists for a time. Exposure of a growing culture to 1 unit of penicillin for 5 min., with removal at the end of that time, produces a stationary phase in the culture, which persists for 3 hrs. Growth is then resumed.