Tests have shown that these compounds actively blocked the spread of Pseudomonas aeruginosa, which is a common bacterium that causes fatal lung infections in people with cystic fibrosis as well as leads to life-threatening blood infections in patients who have serious burns or immune system disorders such as Aids.
Researchers have found that colonies of bacteria use chemical signals to keep a check on their numbers and attack when their populations are large enough to ensure they can overcome a host's immune defenses. When the chemical signals received by the bacteria reach a certain threshold behavior changes dramatically, become aggressive, turning on virulence genes to cause infection. Besides that several bacterial colonies also set up defenses by the secretion of mucus-like substance that forms a slimy, protective "biofilm" around them, which makes them nearly impervious to antibiotics.
In 2002 the US National Institute of Health estimated that over 80% of bacterial infections spread by using biofilms which offer such good protection that very often the bacteria could be killed only by giving the patient a lethal dose of antibiotics.
Researchers at the University of Wisconsin-Madison used microwave-assisted chemistry for designing compounds called N-acylated L-homoserine lactones (AHLs) which although similar to those used by bacteria, differ in that when they come into contact with bacteria they make the bacteria oblivious to their neighbours. As a result, their communication system is cut and the bacteria never get the signal to attack or produce biofilms.
According to Helen Blackwell, the head scientist for the research her group had used the compounds to prolong the lives of organisms infected with Pseudomonas aeruginosa, and had developed finely tuned AHLs to target specific strains of bacteria. These showed promise in the infection in the gut without harming healthy bacteria.
Still more tests are needed to prove the compounds are capable of preventing diseases in humans. Currently they are expected to work best in combination with other antibiotics, by making bacteria more vulnerable.
Dr Blackwell said, "There is an urgent need for new antibacterial therapies. The ability to interfere with bacterial virulence by intercepting bacterial communication networks represents a new therapeutic approach, and is clinically timely."
This research presented yesterday at the annual meeting of the American Chemical Society, in San Francisco has raised hopes for the treatment of some of the most deadly diseases, such as tuberculosis, which infects nearly 15 million people worldwide. Only last week the World Health Organization had warned that a deadly strain of TB which has become virtually untreatable with existing drugs, seemed to be spreading across the globe. Many lives have been lost to extreme drug-resistant TB in several countries.
The compounds that were designed by Dr Blackwell's team are in the early stages of development but is expected to be used to tackle damaging crop and livestock diseases and persistent infections linked to medical implants and catheters.