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BMC Microbiology

, 7:99

First Online: 06 November 2007Received: 14 June 2007Accepted: 06 November 2007


BackgroundCommunity acquired CA methicillin-resistant Staphylococcus aureus MRSA increasingly causes disease worldwide. USA300 has emerged as the predominant clone causing superficial and invasive infections in children and adults in the USA. Epidemiological studies suggest that USA300 is more virulent than other CA-MRSA. The genetic determinants that render virulence and dominance to USA300 remain unclear.

ResultsWe sequenced the genomes of two pediatric USA300 isolates: one CA-MRSA and one CA-methicillin susceptible MSSA, isolated at Texas Children-s Hospital in Houston. DNA sequencing was performed by Sanger dideoxy whole genome shotgun WGS and 454 Life Sciences pyrosequencing strategies. The sequence of the USA300 MRSA strain was rigorously annotated. In USA300-MRSA 2658 chromosomal open reading frames were predicted and 3.1 and 27 kilobase kb plasmids were identified. USA300-MSSA contained a 20 kb plasmid with some homology to the 27 kb plasmid found in USA300-MRSA. Two regions found in US300-MRSA were absent in USA300-MSSA. One of these carried the arginine deiminase operon that appears to have been acquired from S. epidermidis. The USA300 sequence was aligned with other sequenced S. aureus genomes and regions unique to USA300 MRSA were identified.

ConclusionUSA300-MRSA is highly similar to other MRSA strains based on whole genome alignments and gene content, indicating that the differences in pathogenesis are due to subtle changes rather than to large-scale acquisition of virulence factor genes. The USA300 Houston isolate differs from another sequenced USA300 strain isolate, derived from a patient in San Francisco, in plasmid content and a number of sequence polymorphisms. Such differences will provide new insights into the evolution of pathogens.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2180-7-99 contains supplementary material, which is available to authorized users.

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Autor: Sarah K Highlander - Kristina G Hultén - Xiang Qin - Huaiyang Jiang - Shailaja Yerrapragada - Edward O MasonJr - Yue Sh


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