In 2002, three previously distinct species of<unk> , B. infantis,<unk> , and B. suis, were unified into a single species named<unk>  with the biotypes infantis,<unk> , and suis, respectively. This occurred as the three species had extensive DNA similarity including a 16s rRNA gene sequence similarity greater than 97%. In addition, the three original species were phenotypically difficult to distinguish due to different carbohydrate fermentation patterns among strains of the same species. As probiotic activity varies among strains of<unk> , interest exists in the exact classification of new strains, although this is made difficult by the high gene similarity between the three biotypes. Currently, strain identification is done through polymerase chain reaction (PCR) on the subtly different 16s rRNA gene sequences.
Bifidobacterium longum
Bifidobacterium breve
Prevotella bivia
Campylobacter upsaliensis
Bacteroides dorei
Clostridium perfringens
Lactobacillus acidophilus
Clostridium tetani