REDUCE MRSA by getting horizontal

The results of this large cluster-randomized trial of different MRSA prevention strategies are now out in the New England Journal of Medicine, and are being widely (and mostly accurately) reported in all the major media outlets. Those who have followed this blog for any length of time know that we are not surprised at the results. Here’s just a sample of what we’ve written on the topics of active surveillance and the difference between horizontal and vertical infection control strategies.

I can keep this post short, because Mike Edmond and Dick Wenzel have already done my work for me in their excellent accompanying editorial (no subscription required!). I’d mostly like to congratulate and thank Susan Huang (pictured) and her excellent group of collaborators from HCA and CDC for making this very important contribution to the infection prevention literature, a contribution that should have a major impact on prevention practices.

But is it really “case-closed” on universal MRSA active surveillance, as the title of Mike and Dick’s editorial suggests? Every study that has questioned the effectiveness of MRSA screening has been followed by a barrage of letters-to-the-editor questioning the findings, and I suspect that this study will be no different. Later this week I will predict the contents of these future letters with uncanny accuracy. Stay tuned….


  1. We applaud investigators for their hard work in completing a high quality study. However, it has limitations and recommendations are overreaching.

    --The intervention Mupiricin/Chlorhexidine for all patients is very aggressive. Would chlorhexidine alone work in a similar fashion? (resistance is a real concern, especially for mupiricin, and if these agents become inactive they can't be used on high risk patients) We don't really know, but there will be calls to vastly increase antimicrobial exposure to mupiricin based on a study with a mixed intervention that prevented relatively few MRSA clinical cultures even over 74 ICUs I.E. A LOT OF PATIENTS WILL RECEIVE MUPIRICIN FOR A VERY SMALL ABSOLUTE DECREASE IN POSITIVE MRSA CLINICAL CULTURES!

    Bacteremia rates were elevated in the intervention arm during baseline period (6.1 vs. 4.8 or 4.2). Overall bacteremia rate was nearly 50% higher in ICUs that were randomized to the intervention! The intervention itself brought bacteremia rates down to what they already were in other ICUs.

    The effect on bacteremia was mostly skin commensals such as coagulase negative Staphylococcus. As in Climo et al, this is probably the least important organism and may relate to decreasing contamination rates. We think this point is also important in the Climo paper, chlorhexidine bathing only had an effect on VRE acquisition and not MRSA acquisition and only had an effect on coagulase negative Staphylococci and candida bacteremia.

    MRSA Clinical Cultures are a mixed group of colonization/infections that vary depending on sites. Is MRSA in the sputum the same as MRSA in a deep surgical wound? Or urine culture? or superficial wound culture? Did the frequency of culturing change during the intervention. Given data was obtained from a datapull, all of these questions could be answered which would help interpretation of this trial.

    Although the trial is being hailed as a nail in the coffin of active surveillance culturing for MRSA, there are potential harms with over interpretation of the trial. If we begin using mupiricin and chlorhexidine on all ICU patients nationwide, as our European colleagues have suggested will occur, we may eventually have as many problems from the study as early studies of ASC. We also think that one cluster randomized trial should not change practice in such a sweeping manner.

    From a more cautious perspective, this trial and Climo et al support that chlorhexidine bathing likely has a benefit on infections in the ICU. It isn't a huge effect and it is predominantly on markers that aren't as important (MRSA clinical cultures and coagulase negative Staphylocci AND CANDIDA (and VRE for Climo)). However, it should be considered by hospital ICUs with problems in these infections.

    We should be worried that ASC may be finished only to be replaced by an equally problematic mandate (that more than swabbing every patient is actually treating every patient).


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