Abstract
The background to the discovery and commercial development of the first Streptococcus salivarius probiotic is documented. A 40-year search of the genus Streptococcus for a harmless natural antagonist of Streptococcus pyogenes had as its operational basis a simple deferred antagonism "fingerprinting" procedure, the application of which results in each tested strain being accorded an inhibitor production (P)-type and inhibitor sensitivity (S)-type profile. Systematic application of this schema has opened a "Pandora's Box" of novel streptococcal bacteriocin-like inhibitory substances (BLIS). The numerically prominent commensal S. salivarius is proposed to have a pivotal population-modulating role within the oral microbiota of humans. The probiotic strain S. salivarius K12 produces several megaplasmid-encoded BLIS including the lantibiotics salivaricin A and salivaricin B. Strain K12 and other BLIS-producing S. salivarius are currently in use or under development for application to the control of a variety of common maladies and infections of the human oral cavity.