Dark rod-shaped bacteria inside a dog tumour (Image: David L. Huso and Baktiar Karim/Johns Hopkins Department of Pathology)

Your enemy’s enemy could be your friend. Disease-causing bacteria in soil could become an anti-cancer therapy. The microbes shrink tumours in dogs – and seem able to do it in humans too.

Clostridium novyi bacteria thrive in oxygen-poor conditions, where the enzymes they release can puncture and kill mammalian cells. Saurabh Saha of BioMed Valley Discoveries in Kansas City, Missouri, and his colleagues wondered whether they could use the bacteria to selectively kill mammalian cells within cancerous tumours, which often have a poor blood, and thus oxygen, supply.

The team genetically modified C. novyi bacteria into a form that wouldn’t pose a serious health risk, and injected them into the tumours of 16 dogs. Three weeks later, the tumours had shrunk or disappeared in nine of the dogs.


The group has now also tested the bacteria on a 53-year-old woman with tumours in her liver, lungs and the soft tissue in her right shoulder that didn’t respond to standard treatment. They injected the bacteria into the tumour in her shoulder. One month later, it had shrunk.

Symptoms of infection

The bacteria left healthy, oxygen-rich tissue around the tumour intact. In fact, under a microscope, the researchers could see a precise border between the bacterially infected tumour cells and the non-cancerous healthy cells.

The bacteria did induce symptoms commonly seen in bacterial infection, such as fever and nausea, but these were controlled by antibiotics after the tumour size reduced.

“This is the first study to look at the eradication of tumours in humans using bacteria, and the results were promising,” says Saha.

“This is an elegant study,” says Vikas Sukhatme at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston. It could work well on localised tumours, he says – but more research may be needed to demonstrate that the approach can work against cancers that have metastasised.

Saha stresses that the bacteria are not a silver bullet to treat cancer, but used in conjunction with other therapies they may provide another tool in our anticancer armoury. The method is drastically different to conventional chemotherapies, radiation therapies and even personalised cancer treatments, Saha says.

Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.3008982