The agglutination of beta-haemolytic streptococci by lectins

The ability of 25 lectins, isolated from different plants and fungi, to agglutinate 95 clinical isolates of beta-haemolytic streptococci was examined. Cell suspensions were untreated, trypsin-treated or boiled at pH 2.0. None of the 95 untreated cell suspensions gave a visible reaction with any of the lectins. When the cells were trypsinised, 42 strains were agglutinated with one or more lectin and after boiling at pH 2, all the strains were agglutinated. After treatment with trypsin, 20 different agglutination patterns were observed, and after boiling, 19 patterns, four of which were similar. A correlation was found between Lancefield group C and some of these patterns. Some lectins reacted specifically with group C streptococci; DBA and WFA, both specific for D-GalNAc, DSA, a GlcNAc-specific lectin, and RPA, which showed a complex specificity, reacted only with group C strains. Furthermore, the lectin of Maackia amurensis reacted with 50% of group B streptococci only. Agglutination assays with lectins were reproducible, easy to perform, relatively inexpensive and, therefore, applicable to studies of cell-wall structure and epidemiology of beta-haemolytic streptococci.