The Amino Acid Requirements of Penicillin Resistant and Penicillin Sensitive Strains of Micrococcus Pyogenes

Since the classic study of the nitrogen require-ments of Micrococcus pyogenes by Gladstone (1937), there have been relatively few studies on the amino acid requirements of this group of organisms. This investigator showed that a medium containing thiamin and nicotinic acid and 16 amino acids would support the growth of 25 of 26 strains studied. Porter and Pelczar (1941) demonstrated that certain strains of M. pyogenes could be subcultured serially on Glad-stone's amino acid medium only if biotin was added to the medium. Other reports relating to the amino acd requiremets of this group of organisms concern studies of only a few strains carried out for the purpose of correlating no acid metabolism with enterotoxin production (Surglla and Eite, 1946), with sulfonamide resistae (Steers and Sevag, 1949), and penicillin resistance (Gale and Rodwell, 1948). In their study of the amino acid metabolism of penicillin resistant strains of M. pyogene var. aureus, Gale and Rodwell (1948) concluded that resstant strains are able to synthesie the amino acids esential for growth. However, the strains studied by them had been made extremely resist-ant by subcultivation in the presence of increas-ing concentrations of penicillin until the strains were able to grow in a medium containing the antibiotic in a concentration of 6,000 units per ml. Although Bellamy and Klimek (1948) have shown that these same highly resistant mutant cultures produce extacellular penicillinase, there is no evidence to indicate that the enzyme had an esential role in their resistance. In contrast with these "artificially " resistant strains, "nat-urally " resistant strains isolated from clinical infections of man are resistant by virtue of their ability to produce intracellular penicilinae