Bacteria Fighter Goes Where Antibiotics Can't

Researchers at the Technion-Israel Institute of Technology have figured out a way to turn one of natures most powerful microbe fighters into a guided missile that strikes specifically at a common bacteria responsible for serious infections throughout the body.

Professor Amram Mor of the Biotechnology and Food Engineering Faculty and his colleagues revamped an antimicrobial peptide, a small molecule made of short chains of amino acids, that attacks Pseudomonas aeruginosa. P aeruginosa is the bacterium behind serious lung infections in people with cystic fibrosis and some types of pneumonia and meningitis, as well as less serious but widespread infections such as swimmers ear and urinary tract infections.

The research was reported in the Jan. 26, 2007 issue of the journal Chemistry and Biology. Common antibiotic medicines used to treat infections are increasingly thwarted by new strains of drug-resistant bacteria. Unlike most antibiotics, antimicrobial peptides can sidestep such resistance mechanisms and destroy by brute force, often simply ripping a hole in a targeted cell. For this reason, antimicrobial peptides present an obvious advantage over conventional antibiotics, said Mor.

Yet one of the features that makes the peptides so usefultheir ability to kill a variety of invaders from bacteria to cancer cellsmakes them hard to deploy as a treatment against specific infections. Their non-specific action can also destroy normal red blood cells.

The number and order of amino acids in an antimicrobial peptide determines how it recognizes and attacks an invading microbe. Some previous studies have shown that removing amino acids from one end of a peptide can boost its antibacterial properties. However, these shortened peptides are also more deadly to red blood cells.

To build a more useful and less toxic antimicrobial peptide, Mor and colleagues removed a few amino acids from one end of a dermaseptin peptide and replaced it with a fatty acid molecule. (Dermaseptins are a well-known family of peptides that destroy a wide range of microbes). The study shows for the first time that a fatty acid can replace part of a shortened peptide, which may lower the costs of manufacturing such peptides, according to the researchers.

The change made this particular peptide deadly accurate against P. aeruginosa while leaving other bacteria alone. The new peptide was also 60 times less likely to adhere to red blood cells.

Many experts believe that one of the factors that might hamper the commercial use of antimicrobial peptides is their prohibitive cost. Therefore, smaller means cheaper and in this case, more potent, Mor said.

Mor added that the procedure might be used to create a variety of designer peptides that latch on different microbes, and that his lab will work on repeating the strategy with other peptide chains. The researchers also hope to test these new peptides against infections in animals.

Source: American Technion Society