Subtle genetic changes enhance virulence of methicillin resistant and sensitive Staphylococcus aureus

Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA.
BMC Microbiology (Impact Factor: 2.73). 02/2007; 7(1):99. DOI: 10.1186/1471-2180-7-99
Source: DOAJ

ABSTRACT Community 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.
We 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.
USA300-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.

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Available from: George E Fox, Sep 28, 2015
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    Genome Biology and Evolution 03/2014; 6(4). DOI:10.1093/gbe/evu048 · 4.23 Impact Factor
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    • "The isolates that belong to ST1 (which includes the Mid-Western USA clone), ST30 (which includes the South-West Pacific clone), and ST398 (the LA-MRSA) also show considerable differences in gene content with other members of these STs. One can wonder whether it is possible to speak about specific CA-MRSA clones with maybe the exception of USA300, which shows only little gene and sequence variation [25]. It seems more likely that SCCmec was introduced several times in the other STs that are linked to the well-known clones and that their pandemic spread is more limited than assumed. "
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    PLoS ONE 10/2013; 8(10):e78340. DOI:10.1371/journal.pone.0078340 · 3.23 Impact Factor
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    • "Extracellular DNA (eDNA) is another component of the biofilm matrix and the structural role of eDNA in promoting biofilm stability is highly variable and dependent on the bacterial species, growth conditions, and age of the biofilm [61,83–86]. We found DNaseI treatment to have a varying effect on both biofilm inhibition and dispersal. "
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    PLoS ONE 08/2013; 8(8):e73376. DOI:10.1371/journal.pone.0073376 · 3.23 Impact Factor
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