A bacterium isolated from Japanese tree frogs completely removed colorectal tumors in mice after one intravenous treatment. Researchers at the Japan Advanced Institute of Science and Technology found the strain, Ewingella americana, attacked cancer cells directly while also triggering an immune response. The results were published in the journal Gut Microbes in 2025.
The team screened 45 bacterial strains collected from amphibians and reptiles. Nine showed anticancer effects in tests, with E. americana producing the strongest outcome.
In the mouse model a single dose led to a 100 percent complete response rate. The bacterium multiplied inside tumors by about 3,000 times within 24 hours and attracted immune cells that released inflammatory signals such as TNF-α and IFN-γ.
Safety tests showed the bacteria cleared from the blood with a half-life of roughly 1.2 hours and left no trace in healthy organs after 24 hours. Mild inflammation resolved within 72 hours, and no chronic toxicity appeared during a 60-day observation period.
The study was limited to colorectal cancer in mice. Researchers plan to test the approach on other solid tumors and explore combinations with existing treatments.