Preventing S. aureus SSI: Who does what?

Pre-operative (or better peri-operative) treatment of nasal S. aureus carriage is one of the most – if not the most – effective infection prevention measure. A large double-blind randomized controlled trial convincingly confirmed the meta-analysis results of previously performed smaller studies: 5 days of nasal mupirocin ointment together with chlorhexidine showering reduced the incidence of deep-seated S. aureus surgicial site infection (SSI) with 80% among S. aureus carriers undergoing orthopaedic or cardiothoracic surgery. Eight years after publication of these findings I (and others) still have the feeling that many hospitals have not implemented this measure.

In our hospital, we started implementation the “screen & treat” strategy even before publication (as participating study site we knew the results one year ahead of publication….). Yet, replication of study procedures required screening of patients at multiple out-patient clinics or in different hospital wards, frequently with a very narrow window of opportunity as many were referred from other centers. Than the samples needed to be transported to the lab, processed, results needed to be communicated with the staff of many different wards and then patients needed to receive their treatment, in time… At the end of this logistical rollercoaster only few received treatment. For the trial that didn’t matter, as such patients were not eligible for enrolment.

Faced with that dilemma we evaluated costs and effects and concluded that not screening anyone and treating all (“treat-all strategy”), was (far) more cost-effective and feasible, see. Yet, it also implies that many patients without detected nasal S. aureus carriage (80% in the trial) will receive mupirocin nasal ointment for 5 days. This could be considered inappropriate antibiotic use. But what are the risks? If there is no S. aureus, there is no risk that S. aureus becomes resistant. But, if there is coagulase-negative Staph (CoNS) with plasmid-based high-level mupirocin resistance, mupirocin will select these isolates, and the higher numbers may lead to transfer of resistance to S. aureus. But wait a minute, these are either killed by mupirocin or absent. And indeed, in a clinical study we found selection of resistant CoNS when using mupirocin, but no resistant S. aureus, see. Given the current (exremely low) prevalence of mupirocin resistance in S. aureus in our patients, and based on these observations and calculations we decided to replace the failing “screen & treat” strategy with the more feasible “treat-all” strategy. We carefully monitor mupirocin resistance in clinical S. aureus isolates. So far no problems.

I’m wondering how exceptional we are. Therefore, this poll with 2 questions. What is your current practice for patients undergoing orthopaedic or cardiothoracic surgery and what do you think the strategy in your place should be. Three options for both; “do nothing”, “screen & treat”, or “treat all”.

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4 thoughts on “Preventing S. aureus SSI: Who does what?

  1. I read this blog with interest.
    In Nottingham UK we have adopted the universal perioperative decolonisation strategy for cardiac surgery introduced in 2003. We have been monitoring Staph.aureus (SA) bacteraemia cases in cardiac surgery – SSIs, line-infections, occasional VAP. Prior this introduction we had 6-10 episodes of SA bacteraemia per year in cardiac. This dramatically fell during 2003 and the reduction has been sustained ever since. We have had no SA bacteraemia in cardiac surgery for the last 3 years.

    We do have a prevalent highly mupirocin resistant S.epidermidis strain that is found on the cardiac intensive care, and that caused an outbreak of S.epidermidis PVE in 2009 – linked to one surgeon who was colonised too, but have not seem mupirocin resistance emerge in SA.

    For elective orthopaedic surgery we screen pre-op and only decolonise the SA carriers. This has been running for about 4 years. Logistically this is harder than the universal approach, but also seems to be working reasonably well.

    The other areas where we have used a lot of mupirocin decolonisation for many years is within renal dialysis (mainly patient with lines) but have also more recently introduced SA screening for all HD patients. Again, we have not seen very much increase in mupirocin resistant SA in this population.

    Tim Boswell
    Consultant Medical Microbiologist, Nottingham UK

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  2. Thanks for another thought provoking and interesting blog!

    My feeling is we should just treat all but the nagging worry for me is what happens to the coagulase negative staphylococcus population in response? I think the evidence shows that although you generate mupR CoNS this is unlikely to spread to S.aureus (good) – but then you have mupR CoNS in your hospital (not good).
    Tim Boswell above mentions endemicity with mupR S.epidermidis, I also wonder if under the “treat all” scenario do you see more CoNS SSI? Particularly those mupR?

    Liked by 1 person

  3. Two articles, one in Nature, other in PLoS One (Iwase, et al. Staphylococcus epidermidis Esp inhibits Staphylococcus aureus biofilm formation and nasal colonization; Park et al. Intranasal Application of S. epidermidis Prevents Colonization by Methicillin-Resistant Staphylococcus aureus in Mice) reveal that some S. epi strains effectively eliminate S. aureus from the nares. So, potentially unforeseen negative impact of tinkering with nares microbiome can occur.
    Len Mermel

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