It's disheartening, then, to realize that decolonization is not a universally agreed-upon measure, and there is relatively little research that can say in which setting (household, hospital, ICU) it works best, and why. There have been a few studies, and a few review papers summing up studies, on the role that decolonization can play in reducing the risk of infection in already hospitalized, colonized patients — ones about to undergo surgery, for instance. A meta-analysis by the Cochrane group, of 8 trials, found that decolonization in the hospital did reduce the likelihood of infections in surgical patients.
The role that decolonization can play in short-circuiting community infections is much less clear, though there are many, many people who have suffered recurrent infections and testify that it worked for them. (Please speak up in the comments if you are!) One problem is that outside hospitals, there is no one recommended regimen: One physician might tell her patient to use mupirocin and chlorhexdine only, whereas another might tell his patient to also take bleach baths, or bleach all the laundry or household surfaces. The CDC has so far declined to put its muscle behind decolonization in community-strain infections, recommending only that frustrated patients with recurrences seek the advice of an infectious-disease specialist. (See this flowchart of treatment options (.pdf) that the CDC published in 2007.)
Comes now the infectious-diseases division of Evanston Northwestern Healthcare, whom some of you will recognize as being among the most successful and evangelical practitioners of "search and destroy" in the United States. (ENW has recently been renamed NorthShore University HealthSystem and is affiliated with Northwestern University. Disclosure, in case you care: I went to grad school at Northwestern, though not in medicine.) In a paper published in Infection Control and Hospital Epidemiology, the group evaluates the use and success rate of decolonization in ENW/NorthShore's 3 hospitals and finds, well, not such good news: a temporary reduction in patients' being colonized with MRSA, but no success in preventing infection.
This is an important and troubling finding, because decolonization comes with costs. There is the obvious cost to hospitals (and the follow-on cost to insurance companies and consumers) of paying for mupirocin and chlorhexidine themselves. But there is also a hidden cost that we here should be particularly sensitive to: Because mupirocin is being used so lavishly, mupirocin resistance is rising.
In the same issue of ICHE (which, yes, is pronounced Itchy), a related editorial by Dutch researchers reviews the difficulty of conducting decolonization trials, but summarizes the ENW/NorthShore study as not an endorsement of decolonization regimens:
It is clear that staphylococcal carriage is an important risk factor for infection and that eradication of carriage has proven successful for patients who are undergoing elective surgery. For other groups of patients, it is still unclear what the benefits are. It is obvious that indiscriminate use of mupirocin is associated with development of resistance. Therefore, additional studies are warranted to define the optimal MRSA decolonization strategy, including what should be given, to whom, and at what moment and who should guide and supervise the regimen.The cites are:
Robicsek A, Beaumont JL, Thomson RB Jr et al. Topical therapy for methicillin-resistant Staphylococcus aureus colonization: impact on infection risk. Infect Control Hosp Epidemiol. 2009 Jul;30(7):623-32.
Kluytmans J, Harbarth S. Methicillin-resistant Staphylococcus aureus decolonization: "Yes, we can," but will it help? Infect Control Hosp Epidemiol. 2009 Jul;30(7):633-5.