Sunday, May 18, 2008

Nifty Idea For an Antibiotic

Here's something that looks promising:
Phagocyte immune cells that engulf bacteria use defensins to digest their prey. These small molecules are electrically attracted to the bacterium's outer membrane, and fuse with it to create gaping holes that destroy invaders.

The complexity of bacterial cells's outer membranes means they cannot easily evolve to become resistant to defensins. But attempts to harness them for medicine have struggled. Defensins are difficult and expensive to produce, and are typically destroyed by the host's immune system before they can reach an area of infection.

"They are not optimised to circulate around the body," Bill DeGrado, a biochemist at the University of Pennsylvania, Philadelphia, US, told New Scientist. He decided that building his own defensin was the only solution.

His research team stripped down the structure of natural defensins to just the essential membrane-busting components, making one small enough to go undetected by the immune system.


In a standard measure of the risk of bacteria evolving resistance to a new treatment, the defensin outstripped conventional antibiotics.

In the test, a sample of bacteria was given enough compound to kill 90% of the culture, with the survivors used to found a new one. The process was repeated, which drives the bacteria to evolve resistance.

"For conventional antibiotics, you generally find it takes 100 times more of the antibiotic to kill the bacteria after 9 repeats," says Nick Landekic, Polymedix's chief executive. "We've done 14 repeats with PMX-30063 and there is no change in its potency."

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