Penicillin Inhibitor from Staphylococci Which Have Developed Resistance to Penicillin in the Human Body

Abstract

Strains of staphylococci which have developed resistance to penicillin in the human body yield an inhibitor for penicillin. Penicillin inhibitor was not present in 4 strains which had been made highly resistant by exposure in vitro. Resistance developed in vivo was found, among the strains tested, to be a more permanent characteristic of staphylococci than that acquired in vitro.