A young soldier who died after scratching his leg on a bush while out running was killed by a mutated superbug, an inquest heard yesterday.

Richard Campbell-Smith, 18, was training to become a Royal Marine when he picked up the deadly toxin. He was 28 weeks in to his 32-week programme at the Commando Training Centre at Lympstone, Devon, when he became ill after running on Woodbury Common on October 31 last year.

It is thought the infection entered his bloodstream after he suffered bad blisters on his feet and cuts to his legs.

Within a day, the teenager was struggling to walk and was so uncomfortable that he was admitted to the medical centre on the training base. But the infection caused his major organs to fail and he died two days later. A post-mortem examination revealed that he had died of cardiac and respiratory failure.

Yesterday, the microbiologist who gave expert testimony at the inquest into his death said it was the worst bug she had ever seen.

Dr Marina Morgan of the Royal Devon and Exeter hospital also revealed that she had seen two examples in nine weeks and wanted to alert the public and medical profession to the dangers.

The lethal toxin - Panton-Valentine leukocidin (PVL) - has been recorded in America, France and Australia. It kills off white blood cells, leaving the victim unable to fight the infection and is often found in people who have contracted community acquired MRSA.

The super-fit soldier contracted an ordinary bacterium, staphylococcus, that would usually just produce a bit of pus in a graze or cut. But the bug then produced the super-toxin.

Dr Morgan said symptoms often included pneumonia, coughing up blood and very high temperatures.

Dr Elizabeth Earlan, the coroner for Exeter, Devon, recorded a verdict of accidental death and said she would try to ensure that doctors were informed of the superbug.

"I am going to make a recommendation to the medical officer for health that he disseminates information to all doctors in practice updating them on likely symptoms of this infection," she said.

"This is to facilitate early diagnosis and treatment in the hope that mortality of this dreadful infection be reduced."