A MODIFIED strain of bacteria found widely in soil could soon be used to target and kill cancerous tumour cells – leaving healthy tissue unscathed.

The therapy is expected to be tested in cancer patients in two years' time and may lead to a simple but safe procedure for curing solid tumours.

The research has been partly carried out at the University of Nottingham, led by Nigel Minton, Professor of Applied Molecular Microbiology in the Faculty of Medicine and Health Sciences.

Professor Minton said: "This therapy will kill all types of tumour cell. The treatment is superior to a surgical procedure, especially for patients at high risk or with difficult tumour locations.

"If the approach is successfully combined with more traditional approaches, this could increase our chance of winning the battle against cancerous tumours."

The therapy uses a modified form of Clostridium sporogenes, a bacterium which is in the Clostridia group of bacteria. This ancient group of bacteria evolved on the planet before it had an oxygen-rich atmosphere, and they thrive in low oxygen conditions.

When Clostridia spores are injected into a cancer patient, they grow in the tumours, because the tumours are oxygen-depleted environments.

Professor Minton said: "This is a totally natural phenomenon which requires no fundamental alterations and is exquisitely specific. We can exploit this specificity to kill tumour cells but leave healthy tissue unscathed."

When the bacterium reproduces in the tumour, it also produces an enzyme.

An anti-cancer drug is injected separately into the patient and reacts with the enzyme, destroying only the cells in its vicinity – the tumour cells.

Nottingham researchers, together with those from the University of Maastricht, in The Netherlands, have modified the bacterium by introducing a gene into its DNA.

This results in a much-improved version of the enzyme, which can be produced in greater quantities in the tumour than previous versions, and is more efficient at converting the pro-drug into its active form.

The research is being presented at the Society for General Microbiology's Autumn Conference at the University of York, which starts today.

Professor Minton anticipates the strain will be used in a clinical trial in 2013, led by Jan Theys and Philippe Lambin at the University of Maastricht.