Bacillus bifidus: its Characters and Isolation from the Intestine of Infants.

Abstract

1. B. bifidus communis, first isolated and described by Tissier, is the predominant organism in the intestinal flora of healthy breast-fed infants in the early weeks of life. In films of the faeces at this period Gram-positive bacilli may constitute almost 99 per cent. of the organisms present.2. B. bifidus requires fairly strict anaerobic conditions for its isolation in primary culture; but thereafter it grows readily in sub-cultures in the presence of oxygen.3. B. bifidus is a member of the acid-tolerant group of Gram-positive, faecal organisms. Although closely resembling B. acidophilus, it is distinct from the latter morphologically and also in certain of its cultural characters. The results of agglutination reactions indicate that different strains of B. bifidus are not serologically uniform.4. Although B. bifidus is a very pleomorphic organism, no evidence was obtained in the present work that it could be changed into an aerobic, spore-bearing bacillus.5. The predominance of B. bifidus in the intestinal flora of breast-fed infants appears to be closely related to the high degree of acidity of the faeces of these infants. It is probable that the predominance of B. bifidus over other organisms is an important factor in preserving a healthy condition of the intestinal tract in the breast-fed infant.