Methicillin-Resistant Staphylococcus aureus: An Evolving Clinical Challenge

Many medical professionals have experienced firsthand the dramatic increase in Staphylococcus aureus infections—particularly infections with methicillin-resistant S. aureus (MRSA) strains—in their practices. One only has to look at stories in the national and local media about outbreaks of MRSA infection to appreciate how widespread MRSA has become. Recently, Klevens et al. [1], using data from the Active Bacterial Core surveillance system of the Emerging Infections Program Network of the Centers for Disease Control and Prevention, estimated that, in the United States during 2005, there were 94,360 invasive MRSA infections and 18,650 related in-hospital deaths. Clearly, there is a compelling need to better understand the pathogenesis, prevention, and treatment of such infections.

Serious infections due to MRSA, such as endocarditis, pneumonia, and bacteremia, have become more prevalent in the hospital setting. Perhaps more importantly, MRSA infections are now quite commonplace among previously healthy individuals with no or limited exposure to health care settings. So-called community-acquired MRSA (CA-MRSA) infections are now found in many diverse populations of individuals—for example, children and adolescents, athletes, and prison inmates—and manifest in a variety of clinical syndromes, most commonly skin and soft-tissue infections. CA-MRSA strains usually have distinctive genetic profiles, compared with those of hospital-acquired MRSA (HA-MRSA) strains. Moreover, CA-MRSA strains appear to have unique virulence properties and characteristic antibiotic susceptibility profiles that differentiate them from HA-MRSA strains. of great interest, CA-MRSA strains appear to be moving into the health care setting as well, causing nosocomial infections and blurring the clinical and epidemiological distinction between strains.

There is great controversy over the current utility of the “workhorse” antibiotic for treatment of MRSA infections, vancomycin. In fact, vancomycin may no longer be the “automatic antibiotic of choice” for treatment of MRSA infections, because reduced in vitro susceptibility to this agent has emerged and has been correlated with treatment failures. of particular concern, many treatment failures have now been well documented when the vancomycin MICs are at the upper limit of the susceptibility breakpoints. As a result, newer agents approved for treatment of MRSA infection, such as daptomycin and linezolid, are increasingly being used. However, these agents may have limited efficacy for treating certain types of infections (e.g., daptomycin for pulmonary infections), and resistance to these agents has already emerged.

This supplement to Clinical Infectious Diseases is written by a cadre of infectious diseases specialists with particular clinical and research interests in MRSA and is designed to address a number of scientific and clinical questions regarding MRSA. These articles will focus on (a) the current epidemiology of MRSA [2]; (b) the pathogenesis and virulence of MRSA infection, highlighting recent advances in basic and molecular MRSA infection pathogenesis [3]; (c) the latest advances in antibiotic resistance in MRSA [4]; (d) CA-MRSA skin and skin-structure infections and their treatment [5]; (e) the clinical features, diagnosis, and therapies for MRSA pneumonia [6]; and (f) an overview of S. aureus bacteremia with a focus on new therapies and clinical management [7].

The goal of this supplement and educational activity is to provide physicians with the latest information on the diagnosis, treatment, and management of MRSA infections to help them improve the care of their patients.

• © 2008 by the Infectious Diseases Society of America