Save your mupirocin for SSI prevention in cardiac and orthopedic surgery

As our guest blogger, Marc-Oliver Wright, posted last week, widespread use of mupirocin was associated with 400% increase in mupirocin resistance at his hospital. Many are very concerned about widespread and non-selective use of mupirocin as a result of the REDUCE MRSA trial, particularly since the incremental benefit of mupirocin added to CHG is not known. Based on prior studies, it is possible that many of the benefits seen were due to CHG and not necessarily mupirocin.

With that in mind, why should we care about mupirocin resistance? Well, there are instances were mupirocin has more established benefits in the literature and one is in surgical site infection prevention. The issue with most infection prevention intervention studies is that most outcomes like SSIs are rare (fortunately) and research budgets are small, which leads to numerous underpowered quasi-experimental studies. The problem with this type of literature base is that it can lead to unnecessary controversy with clinicians cherry-picking study results to support their specific hypothesis.

To make use of such a literature base and scientifically determine the benefits of nasal decolonization (and other interventions), Marin Schweizer and Loreen Herwaldt at the University of Iowa completed a meta-analysis of SSI prevention intervention studies in cardiac and orthopedic surgery, which was published today in the BMJ (free open access). (COI note: I'm a co-author on the paper and was an independent reviewer/data abstracter) After screening 1423 articles published between 1995 and 2012, they identified 39 studies of moderate to high quality. 17 studies assessed the benefits of nasal decolonization (16 mupirocin and 1 nasal CHG), 15 studied glycopeptide prophylaxis and seven examined the bundle: screening+nasal decolonization+vancomycin). The pooled effects were quite impressive.

Nasal decolonization was associated with a 61% reduction in S. aureus SSIs, a 70% reduction in MRSA SSIs and a 50% reduction in MSSA SSIs. Glycopeptide prophylaxis was associated with a 60% reduction in MRSA SSIs while the full bundle was associated with a significant reduction in S. aureus, MRSA, MSSA and Gram-positive SSIs. I have pasted the table below (click to magnify), but since the full article is open access, you can also read the full article at BMJ.

This meta-analysis guided the implementation of an ongoing trial funded by AHRQ, so more data are coming soon. But what to make of this paper in the context of the recent REDUCE MRSA trial?  I myself am concerned that widespread mupirocin use in all ICU patients will select for resistant S. aureus isolates and render this highly-effective SSI bundle ineffective in short order. It will be sad to watch this example of the 'tragedy of the commons' play out in real time, as I suspect we will. And we will only have ourselves to blame. The data is right before our eyes.