Vancomycin-Resistant Staphylococcus aureus: A Perfect but Geographically Limited Storm?

In this issue of Clinical Infectious Diseases, Sievert et al. [1] provide clinical and epidemiologic details of 7 cases of vancomycin-resistant Staphylococcus aureus (VRSA) infection. They present a scenario of the "perfect storm" in Michigan the right patients, the right organisms, and the right selective pressure resulting in 5 of the 7 reported cases of VRSA infection emerging in that state. In many ways, this scenario is a reflection of the broader issue of antimicrobial resistance, in which local evolution of bacterial strains progresses until a particularly fit strain emerges and then has the possibility of spreading broadly. Some evolutionary steps are more successful than others. For example, the first /3-lactamaseproducing strain of S. aureus was reported in 1941 and eventually spread around the world [2]. Now, >90% of all S. aureus iso-