Putting MRSA to the test

The costs and benefits of screening inpatients for methicillin-resistant Staphylococcus aureus (MRSA) have been widely debated by hospitals and hospitalists. Isolating carriers of the bug is expensive, difficult and not always effective.

What if, however, there were a relatively easy way to identify the patients who are most likely to suffer consequences of a MRSA infection before they've even become infected? A recent study by a group of critical care specialists may have found a strategy for unearthing the ICU patients who will develop MRSA infections.

The researchers, working at Montefiore Medical Center in New York City, used a critical care consult team to identify 200 critically ill patients. All of the patients were tested for MRSA nasal colonization, then followed for 60 days or until hospital discharge. The patients who tested positive for nasal colonization were significantly more likely to develop a MRSA infection (7 infections in 29 people in the colonized group compared to 1 in 171 in the uncolonized group). The study was published in Critical Care Medicine in January.

Considering these and some other recent findings about the effectiveness of decolonization, lead author Adam Keene, MD, believes that such a screening program may provide a means for critical care specialists, hospitalists or both to reduce the burden of MRSA in their ICUs. He recently spoke with ACP Hospitalist.

Q: What motivated this study?

A: As an infectious disease physician and intensivist, I saw the toll of MRSA on the critically ill patients and how poorly those patients did. The patients who develop infection almost always have nasal colonization prior [to becoming infected].

Q: How strong is the correlation between MRSA colonization and infection?

A: I did a similar study at Columbia [University] looking at patients who had already been admitted to the ICU, and we found similar results [to the current study]. About a quarter of patients who have MRSA nasal colonization who come into the ICU will subsequently develop a true MRSA infection.

Q: Is it clear that decolonization effectively prevents infection?

A: There have been a lot of negative prospective trials looking at nasal decolonization for patients with MRSA. [But] if you look at the places where the interventional trials have been done, it's always in patients in much lower-risk groups.

One paper came out in the New England Journal of Medicine in January attempting nasal decolonizations in surgical patients preoperatively. They showed a reduction in surgical- site infections.

Q: Between that trial and your research, is there sufficient evidence that hospitals should start decolonizing ICU patients?

A: I don't think it's proven. [Our] trial's not an interventional trial. I still think a large, randomized, placebo-controlled trial needs to be done. But because we now have some positive data in lower-risk populations, I think it makes sense to start doing it in the highest-risk population.

Q: How would you identify the patients to test for colonization?

A: Any patients you are seeing in the emergency room or on the floors who are sick enough that you are considering admission to an ICU or stepdown unit; particularly patients who are likely to be intubated and have central venous catheters placed.

Q: In your study, patients were identified by a critical care consult team. Is that a necessary component of the intervention?

A: We see every critically ill patient, so I was taking advantage of that. But I don't think your hospital has to have a critical care consult team for this to be done. At a hospital where the hospitalist is in the ICU and on the floor, they are the perfect person to identify the patient.

Q: How would you test the patients for colonization?

A: The PCR (polymerase chain reaction) tests would make sense to use, if your lab can do it and if they can turn it around quick enough. I didn't use [them] in this study because it was just sort of an epidemiologic study and I wasn't going to intervene.

Q: When would this need to be done?

A: If you are going to prevent subsequent infection, you need to do it early. You need to do it before their central lines go in, before they get intubated. Again, this points to the potential benefit of using a rapid diagnostic test for MRSA colonization.

Q: What should clinicians do to decolonize the patients who test positive for MRSA?

A: Mupirocin nasal ointment, with or without chlorhexidine body wash. The data is much better on the mupirocin than on the chlorhexidine body washes.