Capacity of group A, B, C, D, and G streptococci to agglutinate sensitized sheep red cells.

Abstract

The reactivity of streptococci with sheep red cells, sensitized with a subagglutinating dose of rabbit anti‐sheep red cell antibodies was studied; agglutination of sensitized and not non‐sensitized sheep red cells by streptococci was demonstrated in isolates belonging to groups A, B, C, D and G. The frequencies of isolates which had the capacity to agglutinate were 97, 88 and 100 per cent in group A, C and G, but only 47 and 33 in group B and D. The agglutination of sensitized sheep red cells by streptococci diminished after treatment of the streptococci with protease from Streptomyces griseus, but was not affected by pepsin or trypsin treatment. Heating the streptococci at 60°C for 30 minutes and repeated subculturing did not suppress their agglutinating activity. Besides, various streptococcal extracts agglutinated sensitized sheep red cells. The presence of an immunoglobulin G reactivity in streptococci might cause certain difficulties in the serological grouping and typing of streptococci.