Fibrillar strains of <i>Streptococcus sanguis</i> biotype I carry a surface protein which cross‐reacts with Antigen B from <i>Streptococcus mutans</i> Ingbritt

Abstract

Eleven strains of Streptococcus sanguis biotype I carrying peritrichous fibrils and 4 strains with lateral tufts of fibrils were screened for crossreactivity with Antigen B (AgB), a protein with a molecular weight of 190,000, isolated from Streptococcus mutans Ingbritt. An antigen of similar molecular weight, which cross‐reacted serologically with AgB was detected by immunodiffusion, Western blotting and dot immuno‐binding in strains of S. sanguis biotype I with peritrichous fibrils but not in tufted strains. One strain, S. sanguis LGR2 carried dense fibrils (5+ density) and the gold label appeared to be associated with the fibrils. However, over all the strains there was no correlation between the density of fibrils and the amount of AgB labelling. Immunonegative staining confirmed the absence of AgB cross reactivity in the tufted strains of S. sanguis I, although the gold labelled the tuft fibrils non‐specifically. Antigen B was located on the cell surface of S. mutans Ingbritt and the label extended 45.9±9.9 nm from the cell wall although the strain was non‐fibrillar.