Has decolonization played a central role in the decline in UK methicillin-resistant Staphylococcus aureus transmission? A focus on evidence from intensive care

The UK has seen a dramatic reduction in methicillin-resistant Staphylococcus aureus (MRSA) infection and transmission over the past few years in response to the mandatory MRSA bacteraemia surveillance scheme. Healthcare institutions have re-enforced basic infection control practice, such as universal hand hygiene, contact precautions and admission screening; however, the precipitous decline suggests other contributing factors. The intensive care unit (ICU), with its high endemic rates and complex patient population, is an important reservoir for seeding MRSA around the hospital and has understandably been at the forefront of MRSA control programmes. Recent studies from the UK and elsewhere have identified decolonization with agents such as chlorhexidine and mupirocin as having an important and perhaps underappreciated role in reducing ICU MRSA transmission, although evidence is incomplete and no prospective randomized studies have been performed. Chlorhexidine particularly is being recommended in the ICU for an increasing number of indications, including decolonization, universal patient bathing, oropharyngeal antisepsis in ventilated patients and vascular catheter insertion sites. Likewise, although there is little published evidence on decolonization efficacy or practice on UK general wards, it is now recommended for all MRSA-colonized patients and uptake is probably widespread. The recent observation that MRSA strains carrying the antiseptic resistance genes qacA/B can be clinically resistant to chlorhexidine raises a note of caution against its unfettered use. The dissemination of chlorhexidine-resistant MRSA would have implications for the decolonization of individual patients and for preventing transmission.