Friday, January 22, 2010

The MRSA Beat



# 4276


Back in the early 1990s, when I was a computer consultant and software developer, I was commissioned to write a custom nosocomial (Hospital acquired) infection tracking system for a local hospital. 


My familiarity with medical terminology and hospital procedures from my days as a paramedic proved an asset in that project.  And it sparked an ongoing interest on my part in infection control.


The two `big’ concerns back then were ordinary staph infections and nosocomial pneumonia.  MRSA (Methicillin-resistant Staphylococcus aureus), while first identified in 1961, really wasn’t perceived to be the problem that it is now.


Today, HAIs  (Hospital Acquired Infections) take a tremendous toll on patients lives and on health care costs.   


This overview from an eMedicine article by Quoc V Nguyen, MD, Assistant Professor, Department of Pediatrics, New York State Health Department.


Hospital-Acquired Infections


Nosocomial infections are estimated to occur in 5% of all acute-care hospitalizations; the incidence rate is 5 infections per 1,000 patient-days. Based on the 35 million patients admitted to 7,000 acute-care institutions in the United States, the incidence of HAIs is more than 2 million cases per year.2 HAIs result in an additional 26,250 deaths (range 17,500-70,000) and an added expenditure in excess of $4.5 billion.


The impact of HAIs on the health care systems of developed countries is significant and is proportionate to that of the United States.


Nosocomial infections are estimated to more than double the mortality and morbidity risks of any admitted patient and probably result in as many as 70,000 deaths per year in the United States. This is the equivalent of 350,000 years of life lost in the United States.


It isn’t just MRSA today, of course.


C. Difficle, Acinetobacter baumannii, various pneumonias, and even viral infections (influenza) are just a few of the culprits in behind Hospital Acquired Infections.  But MRSA, due to its ever growing incidence, and difficulty in treating, is perhaps of greatest concern.


In order to learn how to control MRSA, it is imperative that scientists learn how it is introduced, and spread, in a hospital environment.


Which brings us to a fascinating report (well, two actually) from Maryn McKenna, whose book on MRSA is due to be published in late March.   


Scientists have created a method to quickly, and in great detail, produce whole genomes of MRSA isolates.


Since these isolates often pick up small, single letter changes (SNPs) to their genetic code as they bounce from one host to the next, it is possible to track (with pretty good precision) the spread of the bacteria within a facility. 


Maryn brings us some of the surprising results in an article for CIDRAP News, along with a follow up on her Superbug blog.


First the CIDRAP piece.


New tool helps trace MRSA's local, global spread

Maryn McKenna * Contributing Writer

Jan 21, 2010 (CIDRAP News) – A multi-national team of researchers has applied a new genomic tool to a 50-year-old bacterial foe, using minute mutations to track the spread of drug-resistant staph both across continents and within a single hospital.


On a global scale, their sleuthing tracked the movement of one clone of methicillin-resistant Staphylococcus aureus (MRSA) back and forth across the planet, pinpointing when individual cases transported infections across national borders to spark new outbreaks. Separately, their method demonstrated that what appeared to be a hospital epidemic of MRSA was not a single outbreak, but rather a mixed event of patient-to-patient transmission of one strain that was accompanied by multiple importations from outside the hospital of similar but unrelated strains.


The work was published today in Science.

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As a follow up to her CIDRAP piece, Maryn has also posted on her Superbug Blog why she thinks this is so important.


Follow the link to read it in its entirety.


MRSA in the journal Science - spread, outbreaks and an argument for active surveillance

I have a story tonight at CIDRAP about a paper published this evening in the journal Science. To respect fair use and make sure my colleagues get clicks, I just quote the story here — but then I want to talk about why I think it's such an important study.

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