Genome sequence of a virulent, methicillin-sensitive Staphylococcus aureus clinical isolate that encodes the Panton-Valentine leukocidin toxin

Abstract number: O41

Faraj L., Snyder L.A.S., Loman N.J., Turner D.P., Pallen M.J., Ala'Aldeen D., James R.

Objective: To determine the genome sequence of a virulent meticillin-sensitive Staphylococcus aureus (MSSA) clinical isolate SANOT01.

Methods: Roche 454 sequencing determined the genome sequence of the clinical isolate at 12 times coverage. Newbler sequence assembly (Roche) generated 10 scaffolds that were annotated using GenDB and compared with other S. aureus genome sequences.

Results: An 11-year-old Asian girl presented with fever and a 1-week history of knee pain following a trivial fall. An MR scan revealed a large subperiosteal abscess around the upper tibia secondary to metaphyseal osteomyelitis. A PVL-positive, MSSA was isolated from blood cultures and pus. The child deteriorated, required repeated debridement and developed septic shock. Further investigation revealed aortic valve endocarditis with an aortic root abscess.

Whole genome sequencing revealed that SANOT01 is the first sequence of an ST30 S. aureus isolate to be determined. SANOT01 is agr type III and carries three coding regions that are not found in any other S. aureus genome sequences. Amongst the unique genes present in these regions is a dihydrofolate reductase gene (dfrG) which is present in addition to the usual dfrB gene. Downstream of the orfX gene, a 6.5 kb remnant of SCCmec type IVc was found. This sequence has only previously been found in the MRSA252 genome sequence where it is located between the orfX and SCCmec type II sequences. MRSA252 is unique in sharing 14 genome regions with S. aureus strain RF122, a causative agent of contagious bovine mastitis. All but one of these 14 genome regions are also present in SANOT01.

Conclusions: Comparison of the genome sequence of SANOT01 and the closely related MRSA252 HA-MRSA (EMRSA-16) isolate reveals new insights in the evolution of both CA-MRSA and HA-MRSA isolates and the link to S. aureus RF122. PVL-encoding MSSA strains can be significant pathogens but are not currently under mandatory surveillance in UK. As the cost of whole genome sequencing falls further it will become feasible to use this technology to monitor the evolution of both MSSA and MRSA in healthcare settings and reveal clinically relevant information that will help to improve patient outcomes.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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