Scientists have found a common food poisoning bug which could help fight cancer.

Researchers in South Korea have looked at how the salmonella bacteria can help the immune system tackle bad cells. Early animal tests have proved so successful that they're now trying to get funding for clinical trials.

The salmonella bacteria can infiltrate tumours and flag the cancer cells for the body’s immune defences, making them a target for attack.

Cancers have evolved ways of evading the immune system and are often left alone because they are not seen as "foreign".

The salmonella strain engineered by South Korean researchers is a million times less potent than the version of the bug that causes food poisoning. 

In mice with bowel cancer, more than half of the animals were completely cured without any side effects.

Professor Joon Haeng Rhee, of Chonnam National University Hwasun Hospital in Jeonnam, South Korea, said "We believe that this was turning tumour-helping immune cells, Dr Jekyll, into tumour-killing ones, Mr Hyde."

This is the first time scientists have used the body’s own response to salmonella to fight cancer. 

The discovery arose from an unrelated study when scientists found that bacteria attacking shellfish produced a protein that triggered a strong immune response. The modified salmonella releases the same protein to spur the immune system into action.

The research was reported in the Science Translational Medicine, one of a family of journals published by the American Association for the Advancement of Science. 

Dr Catherine Pickworth, from Cancer Research UK, says the new research is "promising", but it will be a long process.