While making a presentation at the Society for General Microbiology's Autumn meeting at Trinity College in Dublin, University of Cambridge researchers said that the toxins are manufactured by communities of the hospital superbug Pseudomonas aeruginosa called biofilms, which are up to a thousand times more resistant to antibiotics than free-floating single bacterial cells.
"This is the first time that anyone has successfully proved that the way the bacteria grow - either as a biofilm, or living as individuals - affects the type of proteins they can secrete, and therefore how dangerous they can potentially be to our health," said Dr. Martin Welch from the University of Cambridge, UK.
"Acute diseases caused by bacteria can advance at an astonishing rate and tests have associated these types of disease with free-floating bacteria. Such free-floating bugs often secrete tissue-damaging poisons and enzymes to break down our cells, contributing to the way the disease develops, so it is natural to blame them. By contrast, chronic or long-term infections seem to be associated with biofilms, which were thought to be much less aggressive," added Dr. Welch.
As regards the significance of their findings, the researchers said that they may be very important to the NHS, which spends millions of pounds every year fighting chronic long-term bacterial infections which are incredibly difficult to treat.
"For example, these chronic infections by bacteria are now the major cause of death and serious disability in cystic fibrosis patients - which is the most common lethal inherited disease in the UK and affects about 8,000 people," said Dr Welch.
In cystic fibrosis, the gene defect means that people are very susceptible to a particular group of opportunistic bacteria including Pseudomonas aeruginosa, which is one of the three major hospital superbugs.
Though aggressive antibiotic treatment can usually control the infection in cystic fibrosis, the strain becomes completely resistant to antibiotics, leading to respiratory failure and death, often while still in their thirties.
"We think that the bacteria in a cystic fibrosis sufferer's lungs are partly living in communities called biofilms, and although medical scientists have investigated their strongly antibiotic-resistant properties, very little research has been done to investigate any active contribution the biofilms might have in causing diseases in the first place," said Dr Welch.
It is widely believed that biofilms serve as reservoirs of bacteria that do relatively little harm. The main danger is thought to be from 'blooms' of free living cells that occasionally break away from the biofilm, and cause periods of poor lung function in the cystic fibrosis patients.
"In this scenario, it follows that bacteria in a biofilm will produce fewer disease-causing chemicals than free-living cells of the same type of bacteria, which is a prediction that we can test. We found that, in contrast to expectation, biofilms do indeed produce harmful chemicals. However, the type of tissue-degrading enzymes and toxins made by the biofilm bacteria differ from those produced by free-floating bugs, which may help them to survive attacks by our immune systems," said Dr Welch.
The study has also found that the biofilm bacteria can produce a protein that is similar to one of the active ingredients in rattlesnake venom, which causes the host cells to commit suicide and die, one reason why rattlesnake bites are so dangerous.
The researchers are presently studying the protein to determine whether it functions in the same way.
They have also found evidence that the trigger for the bacteria to start producing such extra virulence factors is turned on very shortly after the biofilm begins to form.
According to them, the proteins and enzymes may be targeted to develop drugs for a variety of uses-including the treatment of hospital superbugs, cancer and cystic fibrosis-once the virulence factors created by the biofilm bacteria are fully identified.