Key points are not available for this paper at this time.
Strains of Staphylococcus aureus vary only slightly in their susceptibility to the antibacterial action of penicillin. By growing the organism in increasing concentrations of penicillin over a long period it was possible to render the organism resistant to penicillin. Similar degrees of increased resistance were found in 4 strains of staphylococci isolated during the course of penicillin therapy for localized infections.
Rammelkamp et al. (1942) studied this question.