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

<p>Abstract</p> <p>Background</p> <p>Community acquired (CA) methicillin-resistant <it>Staphylococcus aureus </it>(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.</p> <p>Results</p> <p>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 <it>S. epidermidis</it>. The USA300 sequence was aligned with other sequenced <it>S. aureus </it>genomes and regions unique to USA300 MRSA were identified.</p> <p>Conclusion</p> <p>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.</p

Paradoxical DNA repair and peroxide resistance gene conservation in Bacillus pumilus SAFR-032.

BACKGROUND: Bacillus spores are notoriously resistant to unfavorable conditions such as UV radiation, gamma-radiation, H2O2, desiccation, chemical disinfection, or starvation. Bacillus pumilus SAFR-032 survives standard decontamination procedures of the Jet Propulsion Lab spacecraft assembly facility, and both spores and vegetative cells of this strain exhibit elevated resistance to UV radiation and H2O2 compared to other Bacillus species. PRINCIPAL FINDINGS: The genome of B. pumilus SAFR-032 was sequenced and annotated. Lists of genes relevant to DNA repair and the oxidative stress response were generated and compared to B. subtilis and B. licheniformis. Differences in conservation of genes, gene order, and protein sequences are highlighted because they potentially explain the extreme resistance phenotype of B. pumilus. The B. pumilus genome includes genes not found in B. subtilis or B. licheniformis and conserved genes with sequence divergence, but paradoxically lacks several genes that function in UV or H2O2 resistance in other Bacillus species. SIGNIFICANCE: This study identifies several candidate genes for further research into UV and H2O2 resistance. These findings will help explain the resistance of B. pumilus and are applicable to understanding sterilization survival strategies of microbes

Linear representations of circular plasmids observed in USA300-HOU-MR (a, b) and USA300-MS (c)

<p><b>Copyright information:</b></p><p>Taken from "Subtle genetic changes enhance virulence of methicillin resistant and sensitive "</p><p>http://www.biomedcentral.com/1471-2180/7/99</p><p>BMC Microbiology 2007;7():99-99.</p><p>Published online 6 Nov 2007</p><p>PMCID:PMC2222628.</p><p></p> Replication and regulatory genes are colored red, recombination/transposition genes are green, antibiotic/heavy metal/bacteriocin resistance genes are blue, other genes are white and hypothetical, conserved hypothetical (CHP) and staphylococcal conserved hypotheticals (SCHP) are colored grey. Horizontal bars indicate the regions of pUSA300-HOU-MR and pUSA300-HOU-MS having homology with other sequenced staphylococcal plasmids

DNA sequence of the promoters in USA300-HOU-MR and FPR3757 showing -10 and -35 sequences (red) and SarA consensus binding sites (boxed)

<p><b>Copyright information:</b></p><p>Taken from "Subtle genetic changes enhance virulence of methicillin resistant and sensitive "</p><p>http://www.biomedcentral.com/1471-2180/7/99</p><p>BMC Microbiology 2007;7():99-99.</p><p>Published online 6 Nov 2007</p><p>PMCID:PMC2222628.</p><p></p