Effect of Dietary Clostridia upon Growth-Promoting Responses of Penicillin.

Abstract

Summary 1. The feeding of penicillin stimulated growth and decreased the Clostridia count per gram of feces in birds maintained in old quarters. 2. Penicillin failed to stimulate growth or decrease the Clostridia count in birds maintained in clean quarters where the Clostridia population was low. 3. The feeding of fecal Clostridia decreased the growth rate of birds reared in clean quarters. This decrease was overcome by addition of penicillin to the diet. The feeding of fecal Clostridia to birds reared in old quarters where the Clostridia population was high failed to depress growth. 5. Penicillin produced a growth stimulation only in cases where there was a decrease in the Clostridia count per gram of feces. This indicated that one explanation for antibiotics stimulating growth is through an action on the anaerobic (Clostridia) microflora.