Function and Metabolic Significance of Penicillin and Bacitracin in the Chick. ∗

Summary

(1) The feeding of penicillin, but not of autoclaved penicillin, stimulated the growth of birds fed an all-vegetable protein diet. The injection of either penicillin or autoclaved penicillin similarly increased growth. (2) Bacitracin when administered orally or parenterally increased the rate of growth. (3) Under the conditions of the experiment reported herein the feeding of penicillin increased the penicillin and aureomycin resistant organisms and increased the yeast count. The parenteral administration of penicillin had no effect on the fecal microflora. Autoclaved penicillin had little effect upon the fecal microflora. Bacitracin when administered orally or parenterally failed to have any effect on the fecal microflora. (4) Since the parenteral administration of antibiotics and autoclaved penicillin increased the rate of growth and yet had little effect on the fecal aerobic microflora count it seems possible that the antibiotics may have stimulated growth by some other mechanism. Thus, it might be surmised that the antibiotic molecule or a fragment of same might act as a metabolite within the body of the bird.