"Leaky" hospitals redux: When HA is CA

The CDC work below and several other papers published recently attribute a good proportion of CA-MRSA to hospital strains that have left the institution in a colonized patient and sickened that patient at some point post-discharge. But several papers presented at the annual meeting of the Society for Healthcare Epidemiology of America underline that MRSA traffic is two-way: Community strains can enter the hospital and cause outbreaks there as well.

Cases in point:

• Between 2004 and 2007, the Medical University of South Carolina in Charleston identified 272 hospital-acquired infections that were caused by USA300, the dominant CA-MRSA clone. That's 21.3% of all HAIs in that hospital in those years. (Lead author K Hardman)
• At Johns Hopkins University in Baltimore, nine out of 757 patients admitted to the pediatric intensive care unit became colonized or infected with MRSA 48 hours or longer after they were admitted. Six of the nine were found to have USA300, and one developed invasive MRSA disease. (Lead author AM Milstone, MD)
• And at New York-Presbyterian Hospital, a 5-day-old baby who had not yet left the hospital became infected with USA300, the first casualty in a complex outbreak involving several MRSA strains that eventually comprised 21 infants (12 colonized and nine with infection; 14 of the 21 with USA300) and 10 mothers (five infected Caesarean incisions, two with breast abscesses, two with mastitis and one with a skin infection; six out of 10 with USA300). (Lead author Jean-Marie Cannon, RN)
  

New news on invasive MRSA rates: headed down?

I am at the annual conference of the Society for Healthcare Epidemiology of America, where authentic news was released Sunday, in a very quiet way.

Last fall, a team of authors from the Centers for Disease Control and Prevention published a paper in the Journal of the American Medical Association that for the first time estimated the burden of invasive MRSA disease in the United States. Using data from the Active Bacterial Core Surveillance System — which comprises nine sites around the country and takes in about 14 million people — the team estimated that the annual incidence of invasive MRSA in the US is 94,360 cases, including 18,650 deaths. In an important (and to some researchers controversial) contribution to defining MRSA disease, the team also estimated that 13.7% of the invasive infections were community-associated, 26.6% were hospital-acquired (which they called "hospital-onset"), and by far the largest proportion, 58.4%, were a new category they called "hospital-acquired, community-onset" — the patients acquired the bug while in the hospital, but did not develop disease until after they were discharged. (Cite: Klevens RM et al., Invasive methicillin-resistant Staphylococcus aureus infections in the United States. JAMA, 2007 Oct 17;298(15):1763-71. Full text here.)

The important event Sunday was the first release of an update to that data, adding a second year of analysis. The news: Hospital-acquired infections declined in a small but significant way, by 8.1% — though community-associated and community-onset cases did not change.

The original paper analyzed data from July 20o4, when the ABC system expanded from a pilot program to the full nine sites, through December 2005. The update both reslices that data and adds fresh numbers: It compares calendar year 2005 to calendar year 2006. It finds small downward trends as well in community-onset and community-associated cases, but judges those trends not statistically significant. But Dr. Scott Fridkin, who presented these numbers and was an author on last fall's paper, said the dip in nosocomial cases is statistically robust and a true decline, though adding a third year of data will make the analysis yet more solid.

The decline is intriguing and raises the question: If infection-control interventions in hospitals are pushing down rates of hospital-acquired cases, then why are "hospital-acquired/community-onset" cases not down as well?

As usual with conference papers, the abstract is not online; the CDC says it will be posted today and I'll update when they do. (NB: The data presented at the conference is actually an update of the data in the abstract, and so when the abstract goes up the numbers will not match; the decline presented today is a few percentage points smaller, due to a re-cut of the data after the abstract was written.)

UPDATE 8 April 08: The abstract is now online here.

(Financial disclosure: I am at SHEA for book research and to participate in a session on interactions between researchers and media. In exchange for that session, the organization paid my airfare.)

CA-MRSA increasing in Denmark

Again from the annual meeting of the Society for General Microbiology, a report that CA-MRSA cases are rising in Denmark, a country with a very low incidence rate of HA-MRSA — about 1% of isolates — thanks to aggressive screening of any patient who has been treated abroad as well as any health care worker who has worked outside the country.

But a team from the Statens Serum Institut in Copenhagen says that is now changing as CA-MRSA moves into the country. From an SGM press release:

"We have managed to hold the frequency of MRSA cases down to under one per cent in Denmark for over 30 years. But in 1997 we recognised the first cases of community acquired MRSA, a new strain independent of hospital and nursing home contacts, in a young adult and two families in a rural town", says Professor [Robert] Skov [of Statens]. "From the families we traced the superbug being transmitted through a kindergarten, a school, a factory and a farm. Between 1999 and 2006 the number of community acquired MRSA infections increased from 11 to 175 a year, making up more than 22% of all MRSA infections, as a rising proportion."

As is commonly the case, the paper presented at the SGM is not online. The press release was carried by the site Medical News Today. It contains no details on whether the cases were identified as CA-MRSA by risk factor or by microbiology, and therefore doesn't answer the obvious question of whether they are truly CA-MRSA, or hospital-acquired/community-onset HAIs.

However: A 2005 paper on which Skov was an author did include typing results, and suggests that Denmark now is seeing cases of a new MRSA type, similar (allowing for the vast difference in scale) to what has happened in the US since the 1990s. From the abstract:

Comparison of the 45 community-onset MRSA (CO-MRSA) infections with the 36 hospital-acquired MRSA (HA-MRSA) infections showed several striking contrasts. Most CO-MRSA were recovered from skin and soft tissue infections caused by isolates carrying the Panton-Valentine leucocidin toxin genes, and the majority (84%) of isolates belonged to a single clonal type, ST80-IV, which has been found in the community in other European countries. Clone ST80-IV could be traced in Denmark back to 1993. ST80-IV was rarely found in HA-MRSA infections.

The paper is Faria, NA et al. Epidemiology of Emerging Methicillin-Resistant Staphylococcus aureus (MRSA) in Denmark: A Nationwide Study in a Country with Low Prevalence of MRSA Infection. J Clin Micro April 2005, 43 (4) 1836-1842. The abstract is here.

Antibiotics and the tragedy of the commons

I've been turfing through the pile of research materials I've gathered over the past two years and finding gems I had forgotten about. Here's one, from a post at Pioneering Ideas, a blog dealing with projects funded by the Robert Wood Johnson Foundation. One of RWJF's projects is "Extending the Cure," which seeks to reframe thinking about antibiotic use and stewardship by viewing them as economic and social-science problems rather than as medical problems.

In a guest post last year, Ramanan Laxminarayan, PhD, a senior fellow at Resources for the Future, explains the central problem in beautifully clear language:

[A]ntibiotic resistance is not always going to show up as a ‘crisis’ type of problem. ...

Sure - a set of circumstances such as a new strain of influenza that facilitates secondary infections such as Staphylococcus aureus that cannot be treated easily would result in a crisis. But the more likely scenario is one where, ten years from now, we are all using antibiotics that cost $1,000 or more a treatment course and none of the cheaper antibiotics work. This has a ripple effect on productivity of other medical technologies such as transplants and surgeries and on overall health care costs and insurance premiums. Since no one insurer is affected differently than others, there is no incentive for anyone to act.

Just as there is not going to be a single ‘day that the oil runs out’ and we have to think of solutions to our energy needs twenty-to- fifty years from now, we also have to start thinking of our antibiotics portfolio twenty-to-fifty years from now.

The full post is here.

Everything old (in drug treatments) is new again

From the annual meeting in Edinburgh this week of the Society for General Microbiology comes an intriguing report of a new use for a very old antimicrobial tool.

The old tool is phages, viruses that infect bacteria and that were used as treatments for bacterial diseases in the pre-antibiotic era. (Does anyone going into medicine read Sinclair Lewis's Arrowsmith any more? The heroic doctor protagonist of that novel uses phages against diphtheria.) Following the development of penicillin, phage work was abandoned in the West but remained an active area of research in the former Soviet Union. (See this Slate.com story for details; this webpage looks like a good phage resource, though I can't figure out who the authors are.)

To be hopelessly reductionist, the upside of phages is that they are less likely to provoke resistance and have few side-effects; the downside is that they have to be precisely tuned to the bacteria they are used against. There is no such thing as "empiric therapy" with phages.

Comes now a team from the University of Strathclyde to say they have found what may be a promising new use for phages: chemically bonding them to polymers that can then be used in sutures and wound dressings to prevent infections in surgical sites and implanted catheters and devices.

The abstract (first author Janice Spencer) is not online, but the BBC has posted a short story based on the press release.

UPDATE: My colleague Nick Kelley at CIDRAP, a phage phanatic (sorry), says this is the best phage page he knows of. The index page has a gorgeous electronmicrograph of a phage inserting its stuff into a bacterium.

CA-MRSA — not just a US problem

One of the mysteries of MRSA research has been the apparent difference in MRSA prevalence in different countries. Hospital-associated MRSA is a well-understood foe in Europe, but identification of CA-MRSA is infrequent. So is CA-MRSA actually less common in other countries, or is that an artifact produced by less surveillance there or more awareness here?

A new journal sheds some light on the question, and also sounds a warning. A team from University College-London's Centre for Infectious Disease Epidemiology analyzed data that are easily available in the UK because the country has a national healthcare system: "hospital episode statistics" (hospital admissions by primary diagnostic code) from 1989 to 2004. The team chose the codes that would indicate admissions for a variety of community-onset staph-related diseases: septicemia, pneumonia, bone and joint infections, and an array of skin and soft-tissue infections.

What they found: Over those 15 years, admits for staph septicemia, pneumonia and scalded-skin syndrome rose 5-fold; abscesses and cellulitis, 3-fold, and bone and joint infections, 1.5-fold. These were much larger increases than in the only national surveillance system which collects voluntary reports just of Staph bacteremia and showed a 2.5-fold increase from 1990 to 2004.

Because the study is based on ICD-9/ICD-10 codes, it contains no microbiological information. However, the authors point out that the invasive diseases captured by the codes are associated with PVL toxin, which in turn is associated with CA-MRSA more than HA-MRSA or MSSA. They say:

We identified a previously undescribed but major increase in pathogenic community-onset staphylococcal disease over the past 15 years. These trends are of concern given the international emergence of invasive community-onset staphylococcal infections.

The paper has been published ahead of print by Emerging Infectious Diseases. The cite is: Hayward A. et al. Increasing hospitalizations and general practice prescriptions for community-onset staphylococcal disease, England. Emerg Infect Dis. 2008 May; [Epub ahead of print]

On personal MRSA stories

I don't write here about MRSA victims' stories, for two reasons. First, there are excellent other sites on the net where MRSA communities have already formed, such as MRSA Resources and MRSA_Support; it seems disrespectful to the leaders of those very vibrant communities to try to duplicate their work.

And second and more selfishly, the roughly 50 victims who have spoken to me so far — with more to come — have done so on the understanding that their stories will appear first in my forthcoming book SUPERBUG. When the book is ready to go and its static site is built, I hope we'll have a page that features victims' stories and invites others to post theirs as well.

That being said, if you've come to this site because you have had MRSA, please get in touch! Post a comment: They are moderated, so I see them first and can take them out of the queue if you prefer to be private. Or email me: My email address is in the profile box on the right.

And with all that said, there is one additional victims' site that I want to recommend. Consumers Union (yes, the people who publish Consumer Reports magazine) has a campaign called Stop Hospital Infections that is pushing for legislation requiring mandatory reporting of all HAIs including MRSA. The site combines advocacy tools with heartbreaking accounts of lives changed; take a look.