Study on the "Streptococcus milleri" Adhesins Involved in Its Colonization to Human Bodies

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Of the 36 "Streptpcoccus milleri" strains tested of various serotypes, only 26 serotype g, g-related or h Streptpcoccus intermedius, Streptococcus constellatus or Streptococcus constellatus strains (21,4 and 1 strains respectively) produced cellular agglutination in human whole saliva filtrate. Cells of S.intermedius 1208-1 (serotype g) but not of S.constellatus NCTC 10708 (b) carried long fibrils which extended radially from cell surface and assumed a curly single strand of 1 mum or longer, suggesting that saliva-indeced cell-aggregating factor (s) may exist on the peritrichous appendage. The fibrils were isolated from cells by sonication and purified by 50% ammonium sulfate precipitation followed by a DEAE-Sepharose CL-6B column chromatography. The purified fibrils were composed of carbohydrate and protein in an approximate weight ratio of 3 : 1. Serine, cysteine and lysine were contained in relatively high proportions (10.0-7.9 mol%) and nonpolar amino acids were detected 38.1 mol%. Carbohydrate moiety was composed of mannose, galactose and their amino derivatives at an approximate molar ratio of 4 : 2 : 1. The fibrillar materials were partially hydrolyzed by papain, pronase-P and subtilisin but not by any glycosidases tested. The purified fibrils possessed the molecular weightof higher than 250 kd and were suggested to be composed of unit monomer of 60kd. The cellular aggregation was inhibited by heat treatment of cells and by the presence of the anti-fibril immunoglobulin Fab fragment or the purified fibril preparation. However, the heat-sensitive cellular aggregation-mediating site was supposed not to be identical to the heat-resistant antigenic determinant of fiblillar molecules. Of the 26 saliva-induced aggregating strains (g, h or g-related), only 20 S.intermedius, S.costellatus or S.anginosus strains, but 6 S.intermedius or S.constellatus strains did not, produced the particular type of fibril detected with S.intermedius 1208-1 (g) cells.