Are the Groups of Beta Hemolytic Streptococci Inter-Transformable?

Abstract

It has been reported 1 that fibrinolysis by Group A hemolytic streptococci was a character of diminishing intensity as one proceeded from the S-culture phase through the R and finally to non-hemolytic colonies showing an exclusively diphtheroid cell-morphology. Moreover, these feebly fibrinolytic diphtheroids possessed an unusual lability, as indicated by their occasional reversion to the identical S-colony type of hemolytic streptococcus (Stoddard strain) from which they had originally dissociated. Such a “reverted” diphtheroid culture agglutinated significantly in the antistreptococcal S-serum and absorbed from this serum the antibodies specific for it.

Subsequently the cultures of this diphtheroid, started from a single cell, have undergone further changes that appear to determine the Lancefield group into which the streptococcus redissociated from this diphtheroid shall fall. These changes have occurred under the following conditions. When this strain was kept for several months in our desiccated stocks and then transferred to semi-solid blood agar at room temperature, 4 transfers being made at monthly intervals, it lost practically all of its fibrinolytic ability. The same strain kept under the same conditions, except that it had been stocked on blood-agar slants in the cold room instead of being desiccated, retained its original fibrinolytic capacity. Inasmuch as Group C strains are usually non-fibrinolytic, the loss of this character might be viewed as the precursor of additional changes that resulted eventually in a strain having the serological reactions of Group C.

The non-fibrinolytic diphtheroid was then transferred to ordinary blood-agar slants which were sealed and put in the cold room (10°C). Transfers were made to the same medium under the same conditions at monthly intervals. In a future paper it will be shown that under these conditions after 5 transfers this strain underwent changes that resulted in its reversion to a hemolytic streptococcus (NF), the characters of which were obviously different from those of the streptococcus (F) that reverted under identical conditions from the fibrinolytic diphtheroid.