Abstract
Starting with sixteen 24-hour-old chicks, the feces were examined for the presence of citrate and non-citrate-using members of the colon-aerogenes group of bacteria for a period of one week. No growths of colon organisms having the ability to utilize citrate as a sole source of carbon were obtained, but small numbers of citrate-using B. aerogenes were found in the feces of nearly all of the chicks.
Eight of these chicks were fed “non-fecal” (citrate-using) B. coli at the rate of two agar slants per chick per day, the organisms being washed off into the milk at the morning and night feedings. All bacteria used were growths from single cell isolations, the coli being soil organisms of the Koser type, 1 and one culture was furnished by Dr. Koser.
During the first three weeks the experiment was conducted under sterile conditions in so far as the colon-aerogenes group was concerned; all food was thoroughly pasteurized, all dishes were sterilized at each feeding, and the chicks were kept in sterile cages containing sterile sand and a layer of sterile shavings. During the latter part of the experiment, sterilization was discontinued since the number of colon-like organisms present in the food, etc., before sterilization was too small to make any difference in the enormous amounts fed to the chicks.
Specimens of feces in the first period were obtained aseptically. A suspension of a portion of the feces from each chick was made in sterile broth, and from this, eosin-methylene-blue-crystal violet-agar 2 plates were streaked. (This medium gave a very sharp differentiation between colon and aerogenes types, but no satisfactory test as between colon types using or not using citrate.) From the colon colonies which appeared on these plates, ten were picked at random and transferred to citrate medium.
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