Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus

Bo Shopsin, Public Health Research Institute and †Department of Microbiology, New York University School of Medicine, New York, New York, USA; Barry N. Kreiswirth, Public Health Research Institute and †Department of Microbiology, New York University School of Medicine, New York, New York, USA.

Disclosures

Emerging Infectious Diseases. 2001;7(2) 

In This Article

Abstract and Introduction

Subtyping methicillin-resistant Staphylococcus aureus (MRSA) isolates and tracking nosocomial infections have evolved from phenotypic to genotypic approaches; most laboratories now depend on pulsed-field gel electrophoresis (PFGE). We discuss the limitations of current image-based genotyping methods, including PFGE, and the advantages (including ease of entering data into a database) of using DNA sequence analysis to control MRSA infections in health-care facilities.

Staphylococcus aureus is a major nosocomial pathogen that causes a range of diseases, including endocarditis, osteomyelitis, pneumonia, toxic-shock syndrome, food poisoning, carbuncles, and boils. In the early 1950s, acquisition and spread of beta-lactamase-producing plasmids thwarted the effectiveness of penicillin for treating S. aureus infections. In 1959, methicillin, a synthetic penicillin, was introduced. However, by 1960, methicillin-resistant S. aureus strains were identified, the direct result of S. aureus's acquiring the mecA gene, which encodes for an altered penicillin-binding protein gene (PBP2a)[1].

By the early 1960s, European hospitals were reporting outbreaks of MRSA infections, and subsequently MRSA clones spread to health-care institutions around the world[2]. In the United States, MRSA is responsible for approximately 25% of nosocomial infections, and reports of community-acquired MRSA infections are increasing[3]. The multidrug-resistant phenotype of MRSA strains and their intrinsic beta-lactam resistance make them difficult and costly to treat[4,5]. In some medical institutions in New York City, MRSA accounts for approximately 29% of nosocomial infections and 50% of associated deaths[5]. Controlling MRSA remains a primary focus of most hospital infection control programs[6].

Bacterial strain typing, or subspeciation, has become an important clinical tool to investigate suspected outbreaks and to evaluate nosocomial transmission. Numerous typing methods focus on discriminating MRSA isolates. We discuss the limitations of current image-based genotyping methods and the advantages of using DNA sequence analysis to control MRSA infections in health-care settings.

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