Antitumor activity of normal intestinal microflora in human and animals

Abstract

In order to investigate the antitumor activity of intestinal microflora, the constitution of normal flora was tested in human, guinea pig and mice. It was clarified that Eubacterium, Bifidobacterium and Bacteriodes were the predominant bacterial genera in humans. In addition, neither Clostridium nor Enterobacteriaceae was detected in guinea pigs and neither Clostridium nor Bifidobacterium was present in mice. Total bacterial count in tumor-bearing mice were reduced in comparison with those in normal mice. Especially, in the ileum of tumor-bearing mice, the incidence of anaerobic bacterial genera was strikingly decreased. From the bacterial found, fifty nine (59) living and killed strains isolated from intestinal microflora were examined for their antitumor activity against Ehrlich ascites tumor. It was observed that 11 of the tested strains had antitumor activity. Four of these had toxicity to the host, and especially, all mice injected with Pseudomonas aeruginosa (TYM-8), died within several days. Eubacterium lentum (TYH-11), Propionibacterium acnes (TYM-28), Proteus mirabilis (TYM-7) and Serratia marcescens (TY-142), in which antitumor activity was recognized in living and formaline-killed bacteria, cured the tumor- bearing mice. The supernatant culture of Serratia marcescens contained apparent antitumor activity.