Staph receptor as drug target.

A molecule that sits on the surface of Staphylococcus aureus, an infectious microbe that's resistant to many antibiotics, might offer a weak spot in the bacterium's defenses, early research suggests. Certain peptides secreted by the bacteria themselves bind to a receptor called AgrC and trigger the bacteria to make toxins. Other peptides shut down the process. Because many bacteria are doing this simultaneously in dose quarters, the process becomes a cell-to-cell communication system that enables the cells to coordinate their actions, says Richard P. Novick of the New York University School of Medicine, who presented the findings.

When researchers injected doses of S. aureus under the skin of mice, the animals developed toxin-induced abscesses at those sites within 2 days. But when mice were concurrently given the bacteria and a dose of a peptide that binds to and shuts down AgrC, toxin production was limited. That bought enough time for the animals' immune systems to dispatch white blood cells that killed the bacteria and prevented abscesses, says Noviek.

The inhibitory effect on the receptor lasts up to 2 days. Oddly, the peptide doesn't last that long in the body. That transience probably dooms the peptide's prospects as a drug, Noviek says. But researchers are already investigating other compounds that might bind to and disable the S. aureus AgrC receptor, he says.--N.S.