Objectives: It has become increasing evident that most bacteria have the capability of producing antimicrobial peptides, the activity of which is principally directed at closely-related bacteria likely to be their competitors in natural ecosystems. The streptococci are a heterogeneous cluster including overt pathogens (eg. S. pyogenes, S. mutans), innocuous commensals (eg. S. salivarius, S. oralis) and others used in food products (eg. S. thermophilus). Probiotics (live microbial supplements providing health benefit) for the oral cavity have been largely overlooked, with the current scientific emphasis on development of strains for the intestinal tract. Although a few intestinal strains and some genetically-engineered Streptococcus mutans strains have been trialled as dental caries preventatives, by and large there have been few attempts to apply indigenous strains to the prevention and treatment of diseases in the oral cavity. The main thrust of our studies has been screening for BLIS targeting pathogens, with the intention of using the purified antimicrobials as therapeutics or the producer organisms as a probiotics for competitive intervention/ prophylaxis.
Methods: Deferred antagonism testing, classical protein purification and reverse genetics were used to define bacteriocin loci. Colonisation studies with human subjects utilizing freeze-dried stabilized S. salivarius in lozenges, powder or chewing gum delivery formats.
Results: The incidence of BLIS production among the oral streptococci varied considerably. Streptococcus mutans and S. salivarius appeared to be prolific producers, whereas S. pyogenes, S. mitis and S. anginosis were less commonly producers. Pilot studies involving BLIS-producing S. salivarius and S. mutans have indicated some efficacy in preventing dental caries, tonsillitis and halitosis.
Conclusions: Our efforts have largely focussed upon applications of BLIS-producing S. salivarius because of their predominance in the oral cavity, their safety record and the diverse array of BLIS they produce.