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 (NIAID) of the National Institutes of Health.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).