Bifidobacterium adolescentis is a helpful bacterium that is an inhabitant of the human intestinal tract. Bifidobacterium adolescentis are normal inhabitants of healthy human and animal intestinal tracts. Colonization of B. adolescentis in the gut occurs immediately after birth. Their population in the gut tends to maintain relative stability until late adulthood, where factors such as diet, stress, and antibiotics causes it to decline. This species was first isolated by Tissier in 1899 in the feces of breast-fed newborns. Tissier was the first to promote the therapeutic use of bifidobacteria for treating infant diarrhea by giving them large doses of bifidobacteria orally. Since then, their presence in the gut has been associated with a healthy microbiota. The correlation between the presence of bifidobacteria and gastrointestinal health has produced numerous studies focusing on gastrointestinal ecology and the health-promoting aspects that bifidobacteria are involved in. Obtaining more information about specific strains of bifidobacteria and their roles in the gastrointestinal tract have been on the rise as these probiotic organisms are being used as food additives, such as dairy products. Their name is derived from the observation that these bacteria often exist in a Y-shaped, or bifid form.
There are currently 29 species of Bifidobacteria that have been described; Five of these, including B. adolescentis, have interested dairy manufacturers in producing "therapeutic fermented milk products" due to their higher survival rates in acidic products. Thus, along with other beneficial intestinal bacteria such as Lactobacillus acidophilus, Lactobacillus casei, Streptococcus thermophilus, and Enterococcus faecium, bifidobacteria have been added into dairy products, most notably yogurt and milk. These "probiotics" make great residents in dairy products because dairy products need to be refrigerated and have a short shelf life, in addition to being a commonly consumed source of nutrients, enabling consumers to reap the many healthy benefits these bacteria provide in improving gastrointestinal health.