Characterization of a strain of community-associated methicillin-resistant Staphylococcus aureus widely disseminated in the United States

Abstract

A highly stable strain of Staphylococcus aureus with a pulsed-field gel electrophoresis type of USA300 and multilocus sequence type 8 has been isolated from patients residing in diverse geographic regions of the United States. This strain, designated USA300-0114, is a major cause of skin and soft tissue infections among persons in community settings, including day care centers and correctional facilities, and among sports teams, Native Americans, men who have sex with men, and military recruits. The organism is typically resistant to penicillin, oxacillin, and erythromycin (the latter mediated by msrA) and carries SCCmec type IVa. This strain is variably resistant to tetracycline [mediated by tet(K)]; several recent isolates have decreased susceptibility to fluoroquinolones. S. aureus USA300-0114 harbors the genes encoding the Panton-Valentine leucocidin toxin. DNA sequence analysis of the direct repeat units within the mec determinant of 30 USA300-0114 isolates revealed differences in only a single isolate. Plasmid analysis identified a common 30-kb plasmid that hybridized with blaZ and msrA probes and a 3.1-kb cryptic plasmid. A 4.3-kb plasmid encoding tet(K) and a 2.6-kb plasmid encoding ermC were observed in a few isolates. DNA microarray analysis was used to determine the genetic loci for a series of virulence factors and genes associated with antimicrobial resistance. Comparative genomics between USA300-0114 and three other S. aureus lineages (USA100, USA400, and USA500) defined a set of USA300-0114-specific genes, which may facilitate the strain's pathogenesis within diverse environments.

Epidemiological Characteristics of Methicillin-Resistant Staphylococcus aureus Isolates from Children with Eczematous Atopic Dermatitis Lesions

“…The most prevalent CA-MRSA clones in the United States have the USA300 pulsotype harboring staphylococcal cassette chromosome mec (SCCmec) IV and PantonValentine leukocidin (42,43). The community-based epidemic of MRSA led us to think that that MRSA became as prevalent as penicillin-resistant S. aureus strains in the community, as suggested previously by Chambers (6).…”

Clinical and economic outcomes in patients with community‐acquired Staphylococcus aureus pneumonia

“…USA300 isolates typically are resistant only to beta-lactam and macrolide antimicrobial agents and contain genes for the PVL toxin, which typically are not present in strains of healthcare-associated MRSA. 23 Recent studies of acute pneumonia with animal models and in humans have suggested that the PVL toxin-alone or in combination with other virulence factors-is associated with the development of necrotizing pneumonia. [24][25][26][27][28][29][30] In our study, 23 patients with MRSA CAP had strains that contained PVL toxin, and these patients had longer stays in hospital and higher total hospital charges than those with MRSA CAP not containing the PVL toxin.…”

Detection of Methicillin-Resistant Staphylococcus aureus by a Duplex Droplet Digital PCR Assay

“…Reference strains were obtained from the American Type Culture Collection and included methicillin-susceptible and meth-icillin-resistant S. aureus strains, as well as coagulase-negative staphylococcal species (Table 1). Additional reference strains representing wellcharacterized U.S. strains of MRSA described by Tenover and Goering (13,14) were obtained from Ashley Robinson. The MRSA strains employed in this study represented five staphylococcal cassette chromosome mec element (SCCmec) types and subtypes (I, II, III, IV, and IVa).…”