Substance Protects Resilient Staph Bacteria

Researchers have identified a promising new target in their fight against a dangerous bacterium that sickens people in hospitals, especially people who receive medical implants such as catheters, artificial joints and heart valves.

A substance found on the surface of Staphylococcus epidermidis has, for the first time, been shown to protect the harmful pathogen from natural human defense mechanisms that would otherwise kill the bacteria, according to scientists at the Rocky Mountain Laboratories (RML), part of the National Institute of Allergy and Infectious Diseases of NIH.

S. epidermidis is one of several hard-to-treat infectious agents that can be transmitted to patients in hospitals via contaminated medical implants. The new report concludes that the substance -- known as poly-gamma-DL-glutamic acid, or PGA -- must be present for S. epidermidis to survive on medical implants. S. epidermidis infections are rarely fatal but can lead to serious conditions such as sepsis (widespread toxic infection) and endocarditis (inflammation of the lining of the heart and its valves).

Because of the ability of PGA to promote resistance to innate immune defenses, learning more about the protein could lead to new treatments for S. epidermidis and related Staphylococcal pathogens that also produce PGA, according to the RML scientists. In addition, they also are hoping that similar research under way elsewhere on Bacillus anthracis -- the infectious agent of anthrax, which also produces PGA -- will complement their work.

The report of the study, led by Michael Otto, will appear in the March edition of The Journal of Clinical Investigation and is now available online.