The strain, called USA300, was isolated in September 2000 and has been implicated in outbreaks of skin and soft tissue infections in healthy individuals in 21 US states, Canada, and Europe. USA300 is associated with unusually invasive disease and is also sometimes resistant to multiple antibiotics.
Françoise Perdreau-Remington, Binh Diep (University of California, San Francisco, CA, USA), and colleagues worked out the genetic sequence of USA300 and compared it to other strains of S aureus, to identify the genes responsible for its distinctive virulence properties. They found that USA300 has incorporated part of the genome of another bacterium Staphylococcus epidermidis into its own genetic make-up. The investigators believe that these incorporated genes enable the strain to evade host immune responses to survive and spread in host tissue. The researchers also report that because these genes are unique markers of USA300 they have been using it as a diagnostic tool to monitor the spread of the strain in hospital and community settings.
Professor Perdreau-Remington states: "USA300 has acquired mobile genetic elements that encode resistance and virulence determinants that could enhance fitness and pathogenicity."
See also accompanying Comment published online today.
Contact: Françoise Perdreau-Remington, PhD, Professor, Department of Medicine, Division of Infectious Diseases, University of California, San Francisco, Director, Molecular Epidemiology Research Laboratory San Francisco General Hospital, 1001 Potrero Ave, Building 100, Room 301, San Francisco , Ca 94110. T) 415 -206 6899 / 3745 fpr@epi-center.ucsf.edu
The Lancet