1 The Kunstadter Laboratories for Pediatric Research and the Department of Bacteriology, Medical Research Institute and Sarah Morris Hospital for Children of Michael Reese Hospital.
A study is made of the relative degrees of in vitro sensitivity to penicillin of various pathogenic bacteria. Different strains vary considerably in their sensitivity to penicillin. The concentrations of penicillin obtained in the serum following varying dosages per unit body weight in infants and children when given in the following forms are reported: crystalline sodium penicillin G in saline given intramuscularly; the same compound of penicillin in gelatin capsules and in cocoa-butter and beeswax suppositories given rectally; crystalline sodium penicillin G in sesame oil given intramuscularly, and crystalline potassium penicillin G in a new type Romansky formula given intramuscularly. The last preparation, when given in doses of 4,000 u./lb., maintained serum penicillin concentrations 24 hours after administration in 94% of cases, which was above the minimum concentration required to inhibit most strains of
and
Str. hemolyticus and of M. pneumoniae, and the serum concentrations obtained with this preparation 12 hours after administration were equal to or above the minimum concentration required to inhibit most strains of Staph. aureus hemolyticus and of meningococcus.