The species Lactobacillus reuteri was recognized and recorded in scientific classifications of lactic acid bacteria, as early as the turn of the 20th century. At this time it was mistakenly grouped as a member of Lactobacillus fermentum. In the1960s, further work by German microbiologist Gerhard Reuter could distinguish Lactobacillus reuteri from Lactobacillus fermentum. Reuter reclassified the species as “Lactobacillus fermentum biotype II”.
Lactobacillus reuteri was eventually identified as a distinct species in 1980 by Kandler et al. They chose the species name “reuteri”, after discoverer Gerhard Reuter, and Lactobacillus reuteri has since been recognized as a separate species within the Lactobacillus genus.
The first strain of Lactobacillus reuteri for human use was isolated in 1990 from the breast milk of a Peruvian mother living in the Andes. This strain was deposited at the American Type Culture Collection (ATCC) as Lactobacillus reuteri SD 2112 (SD = safety deposit), and was later given the number ATCC 55730.
In 2007 Lactobacillus reuteri ATCC 55730 was replaced by the “daughter strain” Lactobacillus reuteri DSM 17938. The only difference between the strains is the loss of two plasmids of ATCC 55730 that carried resistance to tetracycline and lincomycin, respectively.
The new strain Lactobacillus reuteri DSM 17938 can be considered comparable to Lactobacillus reuteri ATCC 55730 in all aspects of probiotic function: genetic sequence information has shown the irrelevance of the genes of the plasmids to the functions of the strain, and also confirmed that all tested probiotic-related functions of Lactobacillus reuteri DSM 17938 are retained from those of Lactobacillus reuteri ATCC 55730.
The commercial name of Lactobacillus reuteri DSM 17938 is Lactobacillus reuteri Protectis. Other human strains that are used commercially are Lactobacillus reuteri ATCC PTA 5289 and ATCC PTA 6475.