Agglutination of "Streptococcus milleri" by lectins

The agglutination of 218 clinical isolates and three ATCC type strains of "Streptococcus milleri" was tested with 25 different lectins from plants and fungi. An agglutination reaction with one or more lectins was observed with 42 isolates when the cells were untreated. After trypsinisation of the bacteria, 109 strains yielded a positive reaction and after boiling the bacterial cells at pH2, 218 isolates were agglutinated. As an overall result of our experiments with untreated, trypsinised and boiled cells, 17, 37 and 45 different agglutination patterns, respectively, were obtained. The lectins from Datura stramonium, Robinia pseudoacacia and Dolichos biflorus agglutinated isolates belonging only to Lancefield group C, being non-reactive with other isolates. These lectins were also found to be specific for "large colony type" streptococci of group C. The use of lectin agglutination in epidemiological and ecological studies of "S. milleri" is discussed.