S. aureus, often referred to simply as "Staph," is common, found on the skin and in the noses of an estimated 30 percent of people worldwide. It is a frequent source of skin infections, which can usually be treated without antibiotics, but it can also cause serious surgical wound infections, bloodstream and bone infections, or pneumonia. The burden of such infections, according to one recent study, is "staggering: almost 12,000 inpatient deaths annually," an estimated 2.7 million days in excess hospital length of stay, and $9.5 billion in excess charges.
Physicians are particularly concerned about S. aureus because of its ability to survive in the presence of antibiotics designed to kill it. In 1972, according to the Centers for Disease Control, only two percent of S. aureus infections were drug-resistant. By 2004, 63 percent had learned to resist the antibiotics commonly used to treat them.
While such methicillin-resistant Staphylococcus aureus (MRSA) infections have long been a problem in hospitals, nursing homes and dialysis centers, more and more healthy people with no apparent risk factors have been turning up in emergency rooms with virulent S. aureus infections acquired from community rather than health care related sources.