Different strains of the Burkholderia cepacia (B. cepacia) bacterium occur naturally in earth and on plants.

It is responsible for serious lung infections in people suffering from cystic fibrosis, and can shorten their life expectancy by as much as 10 years.

However, Dr Anthony Webb, from the cystic fibrosis unit at Wythenshawe Hospital in south Manchester, warned that the infection was increasingly appearing in other patients.

Similar to Legionnaires'

He said that it was important that the medical community was made aware of the potential threat, likening it to the arrival of Legionnaires' Disease, which was completely unknown when people first fell ill in 1976.

Cases are on the increase

Dr Webb told the annual conference of the European Respiratory Society: "Severe infections with B. cepacia have been described in previously healthy individuals."

He said that a recent outbreak had affected 74 intensive care patients in an Arizona hospitals, all of whom had been infected by a contaminated mouthwash.

Another outbreak in a Mississippi hospital involved the infection of 245 patients who were not suffering from cystic fibrosis.

Pesticide worry

Another concern held by scientistscentres on attempts to harness the ability of the bacteria to kill the fungal diseases of crops.

They believe that incorporating the bug into pesticides only heightens the risk of transmission to humans.

Dr Webb said: "The potential use of B. cepacia as a biological pesticide which may act as a potential hazard to humans demonstrates an area of considerable conflict of interest between agricultural microbiologists and medicine."

He added that the bacterium was causing particular concern in the UK as many infections involve the most dangerous strain, known as ET-12 or "UK epidemic strain".

Sufferers of cystic fibrosis are vulnerable to predatory infections like B. cepacia because mucus acculmulates in the lungs.

The infection is highly resistant to many commonly-used antibiotics.

The bacterium which causes Legionnaires' Disease, a dangerous form of pneumonia, was unknown until an outbreak in an American hotel.