Frog Bacterium Ewingella Americana Eliminates Colorectal Tumors in Mice

Bacterial Isolation and Anticancer Screening

Scientists at the Japan Advanced Institute of Science and Technology (JAIST) recently moved beyond traditional microbiome research by isolating specific bacterial strains from the intestines of three amphibian and reptile species: Japanese tree frogs, Japanese fire belly newts, and Japanese grass lizards. The team collected 45 distinct strains to test their efficacy against tumor cells.

After systematic screening, researchers identified nine strains capable of suppressing tumor growth. Among these, Ewingella americana emerged as the most potent candidate. Unlike previous approaches that sought to modify the gut microbiome composition or utilize fecal transplants, this study focused on culturing the bacteria in a laboratory setting for direct intravenous administration.

Dual-Action Mechanism and Tumor Specificity

The therapeutic success of E. americana is attributed to its ability to survive in the unique microenvironment of a tumor. Because the bacteria are facultative anaerobes, they thrive in the oxygen-deprived regions common to solid tumors. According to research reported in the journal Gut Microbes, the bacterial population increased by approximately 3,000-fold within 24 hours of injection.

The treatment functions through two distinct pathways. First, the bacteria directly damage cancer cells through their presence and growth. Second, they act as an immune stimulant. The study noted that the bacteria accumulated almost exclusively within tumor tissues, effectively avoiding healthy organs such as the heart, lungs, kidneys, and liver.

“Mechanistic investigations revealed that E americana functions through a dual-action mechanism: direct tumour cell killing and robust activation of host immunity.”

Study researchers, via Yahoo

Once inside the tumor, the bacteria attracted immune system components—specifically T cells, B cells, and neutrophils—to the site. These cells released inflammatory signaling molecules, including TNF-α and IFN-γ, which further promoted comprehensive tumor destruction as described by the research team.

Safety Profile and Comparative Efficacy

In mouse models of colorectal cancer, the performance of E. americana was compared against standard treatments, including liposomal doxorubicin and immune checkpoint inhibitors like anti-PD-L1 antibodies. The bacterial treatment resulted in a 100 per cent response rate, outperforming these established therapies in the study.

• Rapid Clearance: The bacteria were cleared from the bloodstream with a half-life of roughly 1.2 hours and became undetectable within 24 hours.
• Lack of Toxicity: No bacterial colonization was observed in healthy organs.
• Transient Inflammation: Any resulting inflammation was mild and normalized within 72 hours of administration.

Future Applications for Human Therapeutics

While the findings are currently limited to mouse models, the research team views this as a foundational proof of concept for using non-pathogenic, naturally occurring bacteria in human medicine. The potential to apply this method to other solid tumors, such as melanoma, breast cancer, and pancreatic cancer, is a primary focus for upcoming research phases.

“Our study establishes a foundation for developing naturally occurring, non-pathogenic bacterial therapeutics and underscores the critical importance of microbial biodiversity in advancing cancer treatment strategies.”

Study researchers, via Good News Network

The study highlights that lower vertebrates may harbor numerous uncharacterized bacterial species with similar therapeutic potential, marking a shift toward exploring environmental biodiversity for future medical breakthroughs. Patients or those interested in clinical outcomes should consult with their healthcare providers as this research continues to develop.

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