The cytotoxic effects of hemolytic streptococci on ascites tumor cells.

The effect of living hemolytic streptococci on ascites tumor cells (Sarcoma 37 and Krebs-2 carcinoma) was studied in vitro by phase microscopy and in vivo by implanta tion into mice. The effects produced by Streptococcus pyogenes strains were compared with those of Serraiia marcescena, Sareina lutea, and Streptococcuafuecalis. Three of the eight streptococcal strains were highly effective against the tumor cells, resulting in reduced number of tumor “takes― and reduction of tumor sizes, whereas S. lutea, S. marcescens, and S. faecahs were only partially effective in damaging tumor cells after in vitro incubation. The cytological changes are recorded by phase photomicrography, and the histopathological findings of the tumor implantation sites are described.