The Implantation of Oral and Intestinal Strains of L. acidophilus in the Albino Rat

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Abstract
None of 7 oral or dental strains designated by others as Lacto-bacillus acidophilus were implantable in the intestinal tract of white rats by feeding the organisms cultured in milk. Under the same conditions 4 of 5 rough intestinal strains and all of 5 smooth intestinal strains of L. acidophilus were implantable, indicating differences do exist between dental lactobacilli and typical intestinal L. acidophilus. Rough intestinal L. acidophilus organisms, with one exception, were more readily implanted than S strains and persisted for a longer time following cessation of feeding the organisms. Intestinal strains exhibited a slightly higher tolerance to phenol than dental strains and this was the only biochemical characteristic which correlated with implantation. Lactobacilli, apparently rat strains of L. acidophilus, were isolated from each rat receiving lactobacilli milk cultures as well as from a control rat receiving sterile skimmed milk, emphasizing the necessity of adequately controlling implantation exps. especially when smooth strains of lactobacilli are employed. The organisms of rat origin isolated were designated as L. acidophilus rather than L. bifidus since these results, as well as others on the morphological and biochemical characteristics, would not justify the establishment of 2 distinct spp. for organisms so closely related. The results emphasize that errors are likely to occur in identifying aciduric organisms from the oral cavity as L. acidophilus since biochemical differences between intestinal and oral strains have been shown to exist by other investigations, and this work points out the inability of the oral strains studied to become implanted in the intestinal tract of rats. Such evidence would not justify designation of oral strains of aciduric organisms as L. acidophilus since implantation is a generally accepted characteristic of this species. The results also indicate the need for improved methods of examining L. acidophilus prepns. to include not only identification of organisms but also whether they can be implanted.