RESPONSE OF PENICILLIN-RESISTANT STRAINS OF STAPHYLOCOCCUS AUREUS TO EXTRACTS OF BEEF BRAIN

¹ Division of Experimental Medicine, Institutum Divi Thomas, Cincinnati, Ohio

Infections in mice with a series of 24 proven penicillin-resistant strains of Staphylococcus aureus responded to prophylactic and therapeutic administration of 80% alcohol-precipitated beef brain extract. The turbidity studies on penicil-lin-resistant organisms cultured in the continuous presence of brain extract for periods of 74 and 37 days showed an increased growth as well as a conversion of the yellow S organism to a white R form thus indicating that the organisms were sensitive to the extract throughout the experimental period. Similar studies with organisms cultured in the presence of penicillin demonstrated that the resistance to penicillin was maintained as evidenced by increased turbidity. In vivo tests, after 12 hours, 15 and 30 days, of culture under these experimental conditions demonstrated that the organisms became avirulent in the presence of the brain extract and that this sensitivity to the extract was maintained throughout the experimental period.