Vancomycin-resistant Staphylococcus aureus: a perfect but geographically limited storm?

Received 21 November 2007; accepted 22 November 2007; electronically published 30 January 2008. This information is distributed solely for the purpose of predissemination peer review under applicable information quality guidelines. It has not been formally disseminated by the Centers for Disease Control and Prevention. It does not represent and should not be construed to represent any agency determination or policy. Reprints or correspondence: Dr. Fred C. Tenover, Div. of Healthcare Quality Promotion (G-08), Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, Atlanta, GA 30333 ([email protected]). Clinical Infectious Diseases 2008; 46:675–7 This article is in the public domain, and no copyright is claimed. 1058-4838/2008/4605-0005 DOI: 10.1086/527393 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 firstb-lactamase– producing strain of S. aureus was reported in 1941 and eventually spread around the world [2]. Now, 190% of all S. aureus isolates are penicillin resistant as a result of b-lactamase production. On the other hand, b-lactamase–producing isolates of Enterococcus faecalis emerged in several locales in the United States [3] and disappeared within a few years [4]. Predicting which resistant strains will ultimately survive and disseminate is virtually impossible; predicting that at least some strains will disseminate broadly is a certainty. Thus, the data on VRSA presented in Sievert et al. [1], when considered in light of a series of other reports regarding emerging S. aureus resistance over the past 6 years, provide us with ample cause for reflection on the continuing saga of bacterial evolution. Taken together, the data suggest some good news and some bad news.