OXACILLIN-RESISTANT PHENOTYPES OF STAPHYLOCOCCUS-AUREUS

Infections caused by oxacillin-resistant Staphylococcus aureus are a g rowing problem in the United States, accounting for considerable morbi dity, mortality, and expense. The increasing incidence of these infect ions has led to frequent empiric use of broader spectrum antibiotics t o treat these more resistant pathogens, contributing to further worsen ing of the resistance among gram-positive organisms. Three main mechan isms of oxacillin resistance in S aureus are described: (1) classic re sistance, (2) modified S aureus phenotype, and (3) hyper-beta-lactamas e production. Correctly identifying the mechanism of resistance in S a ureus isolates should lend to substantial changes in antibiotic use an d in infection control protocols. These modifications in clinical prac tices could lead to cost savings, as well as a decreased potential for further antibiotic resistance.