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Published on: 2/3/2008
Last Visited: 2/22/2008
The person at San Francisco General hospital tasked with discovering what is going on at a deeper, molecular level is Diep's colleague and co-author, Francoise Perdreau-Remington.The director of the hospital's molecular epidemiology lab, Perdreau-Remington was recruited from a lab in Germany in 1995 specifically for her expertise as a disease detective.Since the late Nineties she's run dozens of studies on bacterial cultures taken from patients at San Francisco General and other city health clinics, in an attempt to identify the mutations in MRSA that confer antibiotic resistance and govern fitness.It was during this screening process that, in March 2001, she became the first person to see the genetic fingerprint of the clone that would become known as USA300.
'I remember it clearly,' she says. 'I thought, "Uh-oh, we have a problem."'
By 2001, San Francisco General was treating so many boils and abscesses in its emergency room that it was forced to open a special clinic exclusively for skin infections.The clone, which at first Perdreau-Remington labelled 'S', had shown up in three cultures taken from patients who attended this walk-in clinic.But when she examined older specimens in cold storage she discovered that the first known 'S' specimen had come from a man who had visited the hospital as early as September 2000.
Perdreau-Remington shared the information with counterparts in Los Angeles County, where inmates of the largest jail system in the US had been complaining of 'spider bites'.On closer examination, these turned out to be staph, and finding the identical genetic fingerprint, Perdreau-Remington sent her findings to the Centers for Disease Control (CDC), which christened the clone USA300.
In December 2007, an outbreak of severe pneumonia in Louisiana and Georgia killed 10 flu patients, including four children.USA300 was also implicated in that outbreak.By now, Perdreau-Remington had won funding to map the bacteria's complete genome.The specimen she picked was one that appeared the most resistant to treatment - a culture that just happened to have been taken in 2003 from the wrist abscess of a 36-year-old man with HIV who was being treated as part of the hospital's 'Positive Health' outreach programme.She did not know it at the time, but the specimen was one of the very first isolates of the highly drug-resistant USA300 variant now circulating in Castro.
The gene map, published in the Lancet in February 2006, was startling.