Some characteristics of nontypable group A streptococci.

1\1 protein is well established as a determinant of virulence in lhuman infections due to the group A hemolytic streptococcus and as the stimulus for the production of type-specific MA protein antibodies(l). However, there are numerOUS instances documented(2-5) and undocumented, of infections as well as cases of rlheumatic fever and nephritis in wlhiclh strains of group A hemolytic streptococci wliiclh could not be typed serologically witlh the available typing sera were isolated. 'rlTe nontypabilityl of virulent streptococci recovered from patients witl streptococcal inifections or asymptomatic carriers, needs clarification. Perhaps the most important question concerns the acquisition of immunity. If some virulent strains do not contain AM protein, whiat are the implications in regard to protection against subsequent reinfection by the samne strain? A first step is to determine wlhetlher or not nontypable strains of group A streptococci culturecl from infected individuals or carriers contain AM protein. This report dlescribes current efforts to determine wlhethier iionitypable strains of grouLp A liemolytic streptococci recovered from individtuals witlh symptomatic streptococcal infections possess 'M protein and wlhetlher other biological properties of these streptococci, suclh as colonial morplhology, lhyaluronic acid productioni, and enzyme prodtuction, are related to their virulence.