Studies on the Mutation of Streptococcus Fecalis

Abstract

The mutation among 4 species of Enterococci, St. fecalis, St. liquefaciens, St. zymogenes and St. durans has not hitherto been experimentally demonstrated, although they are closely related to one another.
The author could endow the capacity of β-hemolysis to St. fecalis, by means of successive transfer of the cocci together with a minimum amount of aseptic staphylotoxin in the testis of mice belonging to the dd-strain. This mutation was confirmed with 5 strains of St. fecalis, and the hemolysis thus induced was characteristic of that of the II-type of Kobayashi's classification (positive β-hemolysis both on horse and sheep blood). These 5 strains underwent mutation to the III-type of Kobayashi (β-hemolysis on horse blood, and α-hemolysis on sheep blood), when they were seeded on the “total heat sterilized fluid culture of original strain (St. fecalis) ”. The same mutation could also be induced in 4 of the 5 above strains within about a year, when the cocci belonging to the II-type were successively preserved on blood agar slants.
These strains of II-and III-type showed resistence against antibiotics and following typical biological properties of enterococci. They grew in 0.1% methylen blue milk, 6.5% NaCl broth and in the broth at pH 9.6. They were furthermore relatively thermostable, resistant to potassium tellulite, could ferment Mannitol and Esculin and did not produce “soluble hemolysin”.
The mutational strains were indistinguishable from the original strains by precipitation reaction and belonged likewise to the group-D of Lancefield.
All the mutational II and III strains were therefore identified as St. zomogenes and the mutation of St. fecalis to St. zymogenes was thus demonstrated.
According to Kobayashi, hemolytic enterococci should always belong to the III-type, but the author's experiment revealed their possible classification into the II-type. This must be taken into consideration in the application of the classification of Kobayashi.