Maryn McKenna

Journalist and Author

Final report from ICAAC-IDSA 08 (news from ICAAC, 3)

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The ICAAC-IDSA (48th Interscience Conference on Antimicrobial Agents and Chemotherapy and 46th annual meeting of the Infectious Diseases Society of America) meeting ended a week ago, and I’m still thrashing my way through the thousands of abstracts.

Here’s my final, highly unscientific selection of papers that caught my eye:

* Evidence that the community-strain clone USA300 is a formidable pathogen: It first appeared in the San Francisco jail in 2001. By last year, it had become the sole MRSA strain found in the jail — it crowded out all others. (P. Tattevin, abstract C2-225)
* Another paper from the same UCSF research group finds that the emergence of USA300 has caused a dramatic increase in bloodstream infections, most of which are diagnosed in the ER, not after patients are admitted to the hospital. (B. Diep, abstract C2-226)
* And the CDC finds that USA300 is picking up additional resistance factors, to clindamycin, tetracycline and mupirocin, the active ingredient in the decolonization ointment Bactroban. (L. McDougal, abstract C1-166)
* An example of the complexity of “search and destroy,” the active surveillance and testing program that seeks to identify colonized patients before they transmit the bug to others in a health care institution: Patients spread the bug within hours, often before test results judging them positive have been returned from the lab. (S. Chang, abstract K-3379b)
* In addition to the report from Spain I posted on during the meeting, there is a report of emerging linezolid resistance in France. (F. Doucet-Populaire, abstract C1-188)
* And in addition to the abundant new news about MRSA in pork, and “pork-MRSA” or ST 398, in humans, over the past few days, there were reports of MRSA in milk in Brazil (W. Gebreyes, abstract C2-1829) and Turkey (S. Turkyilmaz, abstract C2-1832), and beef and chicken in Korea (YJ Kim, abstract C2-1831), as well as ST 398 itself acquiring resistance to additional drugs. (Kehrenberg, abstract C1-171)
* Echoing many earlier findings that MRSA seems most common among the poor, the poorly housed and the incarcerated, BR Makos of the University of Texas found that children are more likely to be diagnosed with the bug if they are indigent, or from the South (which I imagine is a proxy for lower socio-economic status, since the South is a more rural, more poor region). (abstract G2-1314)
* And finally, to the long list of objects (ER curtains, stethoscopes) that harbor MRSA, here are more: The ultrasound probes in emergency rooms (B. Wessman, abstract K-3377). Also: Dentures. (Ick.) (D. Ready, abstract K-3354)

Outbreak of Zyvox-resistant staph (breaking news from ICAAC 2)

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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.