Prevention of streptococcal pharyngitis by anti-Streptococcus pyogenes bacteriocin-like inhibitory substances (BLIS) produced by Streptococcus salivarius

Abstract

Background & objectives: Streptococcus salivarius is a numerically prominent member of the human oral microbiota that produces a variety of bacteriocin-like inhibitory substances (BLIS) having in vitro inhibitory activity against S. pyogenes. Our previous studies of S. salivarius isolates from children using a deferred antagonism BLIS production (P)-typing scheme showed that the 9 per cent of children having large populations of P-type 677 S. salivarius experienced fewer S. pyogenes acquisitions than either the 11 per cent of children having predominant P-type 226 populations or the 60 per cent of children with largely non-inhibitory (P-type 000) S. salivarius. Amongst the other BLIS P-types detected were a number of strongly-inhibitory (P-type 777) S. salivarius. In the present study the inhibitory agents produced by prototype strains of P-types 226, 677 and 777 S. salivarius are compared.

Methods: The prototype BLIS-producing S. salivarius strains SN, 20P3, and K12 were isolated from tongue swabbings. BLIS P-typing was done using standard procedures. The BLIS molecules were purified and characterized.

Results: S. salivarius SN (P-type 226) produces a heat-labile muramidase. S. salivarius 20P3 (P-type 677) produces the 2315 Da lantibiotic salivaricin A and S. salivarius K12 (P-type 777) produces two lantibiotics; salivaricin A2 (2368 Da) and salivaricin B (2733 Da).

Interpretation & conclusion: The P-type 777 S. salivarius strain produced salivaricin A2 and salivaricin B. The combined production of two anti-S. pyogenes BLIS activities by this strain indicates that it could be adopted as a colonizing strain in bacterial interference trials.