Maryn McKenna

Journalist and Author

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

By Leave a Comment

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)

New drugs for MRSA, at various experimental stages

By Leave a Comment

As you might guess by the name, ICAAC (the Interscience Conference on Antimicrobial Agents and Chemotherapy) features much research on the pharma side of things. There were many research reports this past week on drugs at various stages that I was intending to write up for you, but I just noticed that Reuters got there first and did quite a good job. So consider checking this story, which discusses PTK 0796, iclaprim, ceftobiprole, dalbavancin and televancin:

Two experimental antibiotics appear to work safely against an increasingly common and dangerous form of infection called methicillin-resistant Staphylococcus aureus or MRSA, researchers said on Sunday.
Doctors are clamoring for drugs that can fight the so-called superbug infection, which kills an estimated 19,000 people a year in the United States alone. (Reuters)

An important consideration that is not much discussed: It is not enough just to have new drugs; what we need are new classes of drugs. That’s because, when staph acquires protection against one drug, it is likely to be acquiring protecting against all chemically similar drugs — thus, not just methicillin but all the synthetic penicillins; not just Keflex but all the first-generation (and second- and third-generation) cephalosporins.

Microbes in US meat, but no MRSA

By Leave a Comment

The ICAAC-IDSA meeting has ended, but there are still many abstracts that I have not been through. While I pore over them, though, an interesting paper has just been published that somewhat contradicts earlier research on the presence of MRSA in meat. (Earlier posts are here, here, here, here, here, here, here and here.)

The researchers, from the Warren Alpert Medical School of Brown University and Rhode Island Hospital, bought ground beef, boneless chicken breasts and pork chops from 10 stores in and around Providence. Two stores offered both conventional and “natural” choices, so they bought both, giving them 36 (=[10+2]x3) samples all told. They cultured for MRSA, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase producing Gram-negative bacteria and E. coli 0157:H7.

And they found… almost nothing. Only one samples grew a resistant microbe, the ESBL Gram-negative Serratia fonticola. A secnd level of testing, however, uncovered four samples carrying S. aureus — but all methicillin-sensitive, not MRSA.

So are we in the clear? Not necessarily. It is, as they say themselves, as small study, in which only a third of the samples were pork, though pigs are the animals most associated with MRSA via the strain ST398. And the presence of S. fonticola is troubling, because it not only causes disease directly (in animals and in humans), but also harbors a plasmid that can transfer resistance to other bacterial strains.

Nevertheless, it is a comforting reminder that, though MRSA has been found in meat, it has not been found everywhere. (Or at least, not in Providence.) Still, we shouldn’t let our personal vigilance lapse. The hypothetical danger from MRSA in meat is not that we’ll swallow it, but rather that we’ll be colonized if we handle the raw meat without being careful enough about kitchen hygiene. So keep raw meat away from other food, wash your cutting boards and counters, and (say it with me, now), wash your hands, wash your hands, wash your hands.

The cite is: Philip A. Chan, Sarah E. Wakeman, Adele Angelone and Leonard A. Mermel, Investigation of multi-drug resistant microbes in retail meats. Journal of Food, Agriculture & Environment, Vol.6 (3&4), July-October 2008.

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

By Leave a Comment

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.

ST 398 in New York City – via the Dominican Republic?

By Leave a Comment

Here’s a piece of MRSA news from the ICAAC meeting (see the post just below) that is intriguing enough to deserve its own post.

US and Caribbean researchers have found preliminary evidence of the staph strain ST 398, the animal-origin strain that has caused human illness in the Netherlands and has recently been found in Ontario and Iowa, in Manhattan. How it may have arrived: Via the Dominican Republic.

Th researchers (from Columbia University and Montefiore Medical Center in New York, three institutions in the Dominican Republic and one in Martinique) examine the influence of an “air bridge” — very frequent household travel — that is bringing MRSA and methicillin-sensitive staph back and forth between the Dominican Republic and the immigrant Dominican community at the north end of Manhattan. They compared 81 staph isolates from Dominican Republic residents and 636 from Manhattan residents and, among other findings, say that 6 Dominican strains and 13 Manhattan strains were ST398.

It is the first time ST398 has been found in Manhattan or in the Dominican Republic. (Most likely also the first time anyone has looked.)

The authors observe with some understatement:

Given the history of ST398’s rapid dissemination in the Netherlands, its history of methicillin-resistance and its ability to cause infections in both hospital and community, it will be important to monitor its prevalence in these new regions.

It is important to note that these ST398s were not MRSA — they were MSSA, methicillin-sensitive. However: Earlier this year, the Dutch researchers who have delineated the emergence of ST398 in Holland commented on the diversity of ST398 they have found on different pig farms and hypothesized that the resistance element has been acquired several different times by methicillin-sensitive staph. (van Duijkeren, E. et al. Vet Microbiol 2008 Jan 25; 126(4): 383-9.)

So it is possible to hypothesize that this strain arrived in Manhattan from the more rural Dominican Republic, though with the growth of hobby urban farming in NYC, one could also make the case that transmission went the other way. And it is also possible — I emphasize possible — that this could be a precursor to ST398 MRSA emerging in Manhattan. An interesting thought.

(This research is not online, because it is a poster presented at a medical meeting. For reference, the cite is: C. DuMortier, B. Taylor, J. E. Sanchez et al. “Evidence of S. aureus Transmission Between the USA and the Dominican Republic.” Poster C2-224. 48th ICAAC-46th IDSA, Washington DC, 24-28 Oct 2008.)

Breaking MRSA news from the ICAAC meeting 1

By Leave a Comment

There are 15,000+ people at the 48th Interscience Conference on Antimicrobial Agents and Chemistry (known as ICAAC – yes, “Ick-ack”) and 46th Infectious Diseases Society of America Annual Meeting, and at least half of them seem interested in MRSA. At the keynote address last night, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at NIH, referred to MRSA as a “global pandemic.”

Here are some highlights — a few of very, very many — from the first two days:

  • MRSA is truly a global phenomenon: Researchers here are reporting on local epidemics in Argentina, Australia, Botswana, Canada, Colombia, Ecuador, Greece, Japan, Nigeria, Peru, South Korea, Sweden and Taiwan.
  • In the United States, USA300 — the virulent community strain that is crowding out all other community strains — continues its dominance. It first appeared in the San Francisco jail in 2001 and now is the only cause of community MRSA infections there. (Tattevin, P. et al. “What Happened After the Introduction of USA300 in Correctional Facilities?” Poster C2-225.)
  • And MRSA continues to demonstrate its protean ability to cause unexpected forms of illness: The number of cases of sinusitis caused by MRSA seen at Georgetown University tripled between 2001-03 and 2004-06. (I. Brook and J. Hausfeld. “Increase in the Frequency of Recovery of Methicillin-Resistant Staphylococcus aureus in Acute and Chronic Maxillary Sinusitis.” Poster C2-228.)
  • Meanwhile, treatment options are shrinking. Hospitalization for vancomycin-resistant pathogens (that is, resistant to vancomycin, the drug of last resort for MRSA) doubled between 2003 and 2005 according to national healthcare utilization databases. (A.M. Ramsey et al. “The Growing Burden of Vancomycin Resistance in US Hospitals, 2000-2005.” Poster K-560.)
  • But, new drugs are beginning to emerge from the pipeline. Early results from a privately held company called Paratek Pharmaceuticals (co-founded by resistance guru Dr. Stuart Levy) showed that their new tetracycline relative PTK 0796 scored as well or slightly better than linezolid (Zyvox) in safety, tolerability and adverse events, and is advancing to a full Phase 3 trial. (R.D. Arbeit et al. “Safety and Efficacy of PTK 0796.” Poster L-1515.)

More as the meeting goes on.