The Value of Certain Tests in the Differentiation of Lactobacillus bulgaricus from Lactobacillus acidophilus.

At the 1920 meeting of the Society of American Bacteriologists a paper, published only in abstract form (Sherman, 1921), presented some characteristics of Lactobacillus bulgaricus, differentiating this organism from certain other lactobacilli. Eighteen cultures of Lactobacillus bulgaricus were then studied; a number of Lactobacillus casei; a few cultures from feces, assumed to belong to the Lactobacillus acidophilus group; and one "authentic" culture, each, of Lactobacillus acidophilus and Lactobacillus bifidus. The supposed culture of Lactobacillus bifidus appeared to be entirely similar to the culture of Lactobacillus acidophilus. The gas-producing lactobacilli were not included in the study, nor the homofermentative Lactobacillus delbrueckii group. As this work was done before the intensive studies of Lactobacillus acidophilus, the doubt then existing concerning the identity of this organism, and the question of whether or not it was really represented in our collection, made inadvisable the publication of the data in full. However, continued study of authentic cultures of Lactobacillus bulgaricus, and of Lactobactllus acidophiltus, obtained from qualified specialists, convinced us that the tests then indicated are of value in the differentiation of these species. There is no longer need for confusing the Lactobacillus casei group with the acidophilus-bulgaricus groups and other members of the lactobacilli which grow at relatively high temperatures. This paper will discuss the differentiation of Lactobacillus bulgari-