The Growing Menace of Community-Acquired Methicillin-Resistant Staphylococcus aureus

As we read anxiously about the possibility of a worldwide pandemic of avian influenza, another epidemic is actually happening in the United States and elsewhere. Methicillin-resistant strains of Staphylococcus aureus (MRSA) have now emerged as community-acquired pathogens capable of causing serious disease. We have known about MRSA since the early 1960s (1). Until recently, however, infection with these strains was primarily limited to hospitals and other institutional settings. Sporadic reports of community-acquired (or community-associated) MRSA infections have appeared since 1980, but 1999 marked the beginning of the current epidemic in the United States. The sentinel event was a series of fatal cases of community-acquired MRSA infections due to a clone of MRSA known as USA 400 in Native American children living in the Midwest (2). The USA 400 type has subsequently caused infections throughout the country.

A second clone, USA 300, has rapidly established predominance in Atlanta, Georgia (and elsewhere), as clearly demonstrated in the article in this issue by King and colleagues (3). The authors based their findings on a study of 384 persons in Atlanta. Each person had documented community-acquired skin and soft-tissue infections due to S. aureus, and 63% of these infections were community-acquired MRSA. More strikingly, 99% of the community-acquired MRSA isolates were the USA 300 clone. Not surprisingly, two thirds of these cases had inadequate initial therapy, presumably because the attending physicians did not recognize the possibility that the organisms were methicillin-resistant. The proliferation of community-acquired MRSA and especially the USA 300 clone in the United States has been truly remarkable. In other parts of the United States, 60% to 75% of all community-acquired isolates of S. aureus are now methicillin-resistant (4). Because these organisms can infect healthy people in the community, they are a growing threat. To help physicians …