Primary sources of probiotic cultures

Probiotic research has exploded at nearly an exponential rate over the last 15 years, since the first workable definition for probiotics was proposed. This definition, proposed by Fuller (1), was “a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance.” Although this definition is still workable in many instances today, an expanding application list for probiotics has resulted in many new variations of the definition being proposed. These variations take into account such applications as benefits to the host outside its microbial balance and applications other than feed, such as topical applications for probiotics. This recent explosion in probiotic research would lead one to think that probiotics are a relatively new concept. However, the concept has been around for 100 years, from the studies of lactobacilli in soured milks by Elie Metchnikoff (2) and the treatment of infant diarrhea with bifidobacteria by Tissier (3). The resurgence is primarily due to a better understanding of the intestinal microorganisms and their effect on intestinal health.