Effect of Orally Administered Penicillin-Resistant Microorganisms on Growth of Chicks.

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Abstract
Pure cultures of Escherichia coli and Aerobacter aerogenes were grown, lyophilized, and fed to chicks as dietary supplements both in the presence and in the absence of procaine penicillin G. Little or no chick growth response was obtained when either of these organisms were added to the ration in the absence of the antibiotic. Greater gains were obtained when 10 ppm. of procaine penicillin G were fed. When viable cultures of A. aerogenes and E. coli were fed in combination with penicillin, growth was further increased significantly. The effectiveness of the antibiotic in promoting chick growth was increased 64% and 80% when these organisms were added to the feed. The results obtained illustrate the influence of bacterial environment on the antibiotic growth effect and in nutritional studies.