A Fibrinogen Precipitating Factor (FPF) of Group A Streptococci

Abstract

Summary 1) An active factor was found in streptococci which precipitates various mammalian plasmas, and human and bovine fibrinogens. Fibrinogen precipitating factor (FPF) was found in crude acid extracts of several strains of group A. and one strain of group G streptococci; extracts of staphylococci, pneumococci, and viridans streptococci have proven non-reactive. 2) Streptococcal M protein and FPF appear inseparable, although presence of hyaluronic acid in a suspension of streptococcal cells prior to acid extraction may inhibit the fibrinogen precipitating reactivity of the extract, without significantly affecting the typing reaction. FPF and staphylocoagulase share certain properties, but they are not analogous.