Staphylococcus aureus is a bacterium that causes illnesses ranging from minor skin infections[?] and abscesses to life-threatening diseases such as pneumonia, meningitis, and septicemia. Each year some 500,000 patients in American hospitals contract a staphylococcal infection. By changing its chemical makeup slightly to evade attack, S. aureus has become resistant to many commonly used antibiotics. In 1997, physicians were alarmed to encounter staph strains that resist even vancomycin, which used to work when all else failed.
