[Streptococcal group A carriage: new data on the characteristics of the biology of the causative agent and of the immune response of the host].

Carriership of group A streptococcus (A-STR) was registered with significantly greater frequency among children of preschool and early school age (29.8%) than among adults (4.0%). Cultures of A-STR isolated from carriers were characterized by their low capacity for secreting erythrogenic toxin of type A (ET-A), lipoteichoic acid and by lower content of surface proteins than those isolated from tonsillitis and scarlet fever patients. Highly hydrophobic strains of A-STR prevailed in long-time carriers and patients. Elevated immunological characteristics for group-specific polysaccharide A and ET-A were more frequently detected in children than in adults, which correlated with frequency of A-STR carriership in these groups and the capacity of the infective agent to produce ET-A. Some specific features in the character of humoral immune response in carriers, manifested mainly by defects of local immunity (a low level of SIgA to polysaccharide A), were established.