Methicillin-Resistant Staphylococcus aureus Sequence Type 239-III, Ohio, USA, 2007–20091 - - Emerging Infectious Disease journal - CDC
Methicillin-Resistant Staphylococcus aureus Sequence Type 239-III, Ohio, USA, 2007–20091
Suggested citation for this article
Staphylococcus aureus is a major human pathogen that possesses multiple toxins and virulence mechanisms (1). Antimicrobial drug resistance in S. aureus has added to the complexity of treating serious infections caused by this bacteria, and methicillin-resistant S. aureus (MRSA) appears to have greater virulence than methicillin-susceptible strains (2,3). Most MRSA strains in the United States are pulsed-field gel electrophoresis (PFGE) types USA100 and USA300, corresponding to multilocus sequence typing (MLST) ST5 and ST8, respectively (4). MRSA belonging to MLST ST239 and harboring staphylococcal cassette chromosome mec (SCCmec) type III (MRSA ST239-III) are associated with infections in health care settings, outbreaks, increased resistance to antimicrobial drugs, and capacity for invasive disease (5–7).
AbstractMethicillin-resistant Staphylococcus aureus (MRSA) is a human pathogen that has diverse molecular heterogeneity. Most MRSA strains in the United States are pulsed-field gel electrophoresis USA100 sequence type (ST) 5 and USA300 ST8. Infections with MRSA ST239-III are common and found during health care–associated outbreaks. However, this strain has been rarely reported in the United States. As part of a study supported by the Prevention Epicenter Program of the Centers for Disease Control and Prevention (Atlanta, GA, USA), which evaluated transmission of MRSA among hospitals in Ohio, molecular typing identified 78 (6%) of 1,286 patients with MRSA ST239-III infections. Ninety-five percent (74/78) of these infections were health care associated, and 65% (51/78) of patients had histories of invasive device use. The crude case-fatality rate was 22% (17/78). Identification of these strains, which belong to a virulent clonal group, emphasizes the need for molecular surveillance.
MRSA ST239-III has a history of successful dissemination in many regions, leading to a diverse array of regionally prevalent clones. These clones include the Brazilian; British Epidemic 1, 4, 7, 9, and 11; Canadian Epidemic 3/Punjab; Czech; Eastern Australian 2 and 3; Georgian; Hungarian; Lublin; Nanjing/Taipei (ST241); Portuguese; and Vienna clones (8,9). Although it is common worldwide, MRSA ST239-III has not played any predominant role in the United States; infections with MRSA ST239-III have been rarely reported in the United States since the 1990s (9–13). Recently, only 2 reports of this strain in the United States involving sporadic nasal colonization and bloodstream infections have been published (13,14).
In this study, we describe clinical epidemiologic characteristics and molecular analysis of clinical infections with MRSA ST239-III in the midwestern United States. Identification of a strain from such a virulent clonal group in the United States with wide dissemination in other parts of the world represents a potential public health concern.