ANTITUMOR EFFECT OF BIFIDOBACTERIUM INFANTIS IN MICE

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Bifidobacterium infantis is a gram-positive anaerobic bacterium isolated from the feces of human infants. Studies were made on its antitumor effect on cells of an ascites Meth-A tumor induced in a BALB/c mouse with 3-methylcholanthrene. The effect of intraregional injection of this bacteria on subcutaneously transplanted tumor (25 × 10³) produced a complete regression in all the mice, when treatment with B. infantis was started from one day after tumor inoculation for 6 times, where control mice were all dead. The majority of surviving mice rejected the rechallenge of the tumor by this treatment. When tumor cells mixed with B. infantis were inoculated subcutaneously into mice, tumor did not grow in a majority of the recipient mice, but these surviving mice accepted rechallenge of the tumor. Intraperitoneal injection of B. infantis against intraperitoneally transplanted tumor also exhibited a remarkable antitumor effect. The effect decreased as the dosage of B. infantis decreased.