Physicians from Madrid reported today on what's believed to be the first outbreak of MRSA caused by a strain that was resistant to linezolid, usually known as Zyvox, a relatively new and costly drug that is used for complicated MRSA infections and when older drugs fail.
Linezolid resistance in single cases has been recorded before — the first isolate I can see in a quick scan of the literature dates to 2002 — but this appears to be the first outbreak.
Dr. Miguel Sanchez of the Hospital Clinico San Carlos said the outbreak was discovered April 13, 2008 in an ICU patient and subsequently spread to 11 other patients in the ICU and two elsewhere in the hospital. The patients, 8 men and 4 women, had been in the unit for at least three weeks for a variety of reasons; they were intubated, had central venous catheters, and had been receiving broad-spectrum antibiotics. None of them were colonized with MRSA on admission. The outbreak went on for 12 weeks, until June 27.
It was eventually shut down by a combination of strategies: taking the patients off linezolid in favor of other anti-staph drugs (vancomycin and tigecycline); drastically restricting linezolid use, a policy that is already followed by many US hospitals; checking the patients very frequently for colonization; and cohorting them, which means grouping them together physically, away from uninfected patients, and putting them under isolation.
In a quick briefing with reporters, Sanchez seemed to suggest that the hospital does not believe its infection control failed. The hospital swabbed 91 environmental surfaces (such as bed rails and room furniture) and the hands of 47 health-care personnel and found only one sample that grew the linezolid-resistant strain on a culture. A case-control study to find the cause is being conducted, he said.
Half of the patients died, he said, but not as a result of the linezolid-resistant strain.
Sanchez' data slides were not available to reporters this evening. (More precisely, they were delivered to the press room, but in a format that wasn't readable). I'll update with more details if/when we get access to them. Meanwhile, the cite is: M. De la Torre, M. Sanchez, G. Morales et al. "Outbreak of Linezolid-Resistant Staphylococcus aureus in Intensive Care." Abstract C2-1835a.