Selective effects of histidine‐rich polypeptides on the aggregation and viability of Streptococcus mutans and Streptococcus sanguis

Abstract

Enriched preparations of histidine‐rich polypeptides (HRPs) and isolated HRP pairs (1–2, 3–4 and 5–6) degrade in the presence of fresh autologous whole saliva to a series of low‐molecular‐weight cationic peptides (HRPs 6a–c and 7). Analysis of the HRPs during degradation indicates that: HRP 1 is not the parent molecule of the HRPs; the HRP pairs do not convert to each other in a cascade‐like sequence in saliva; and the HRPs can be separated into 2 groups consisting of HRps 1–2 and 3–7. Preparations containing HRPs 1–7, 1–2, and 3–7 were obtained by fractionation and separation on Bio‐Rex 70, and tested for aggregating and antibacterial effects against Streptococcus mutans BHT, S. mutans GS‐5 and Streptococcus sanguis G9B. HRPs 1–2 had significant aggregating effects on all 3 strains but the other HRPs had little to no agglutinating ability. The HRPs did not inhibit the growth of S. sanguis , and HRPs 1–2 enhanced its growth. No growth enhancement by the HRPs was observed for the 2 S. mutans strains. However, significant bacterial inhibition of the S. mutans strains was noted after incubation with HRPs 3–7. The data suggest that the dissimilar effects of HRPs 1–2 and 3–7 may be of importance in the colonization and growth of S. mutants and S. sanguis in vivo.