Meticillin-resistant Staphylococcus aureus (MRSA): screening and decolonisation

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Abstract

Meticillin-resistant Staphylococcus aureus (MRSA) infections are of increasing importance to clinicians, public health agencies and governments. Prevention and control strategies must address sources in healthcare settings, the community and livestock. This document presents the conclusions of a European Consensus Conference on the role of screening and decolonisation in the control of MRSA infection. The conference was held in Rome on 5–6 March 2010 and was organised jointly by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC). In an environment where MRSA is endemic, universal or targeted screening of patients to detect colonisation was considered to be an essential pillar of any MRSA control programme, along with the option of decolonising carriers dependent on relative risk of infection, either to self or others, in a specific setting. Staff screening may be useful but is problematic as it needs to distinguish between transient carriage and longer-term colonisation. The consequences of identification of MRSA-positive staff may have important effects on morale and the ability to maintain staffing levels. The role of environmental contamination in MRSA infection is unclear, but screening may be helpful as an audit of hygiene procedures. In all situations, screening procedures and decolonisation carry a significant cost burden, the clinical value of which requires careful evaluation. European initiatives designed to provide further information on the cost/benefit value of particular strategies in the control of infection, including those involving MRSA, are in progress.

Introduction

Whilst the problem of antimicrobial resistance is widespread amongst common bacterial pathogens, the particular health threat caused by meticillin-resistant Staphylococcus aureus (MRSA) is of increasing concern to clinicians, public health agencies, governments and, last but not least, the general public. This has brought critical attention to bear on the adequacy of current infection prevention and control strategies, which have had to take into account reservoirs of MRSA in healthcare delivery institutions [healthcare-associated MRSA (HCA-MRSA)] and, more recently, the community [community-acquired/associated MRSA (CA-MRSA)] and livestock [livestock-associated (LA-MRSA)] [1], [2], [3], [4], [5], [6]. For these reasons, the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC) organised a joint expert meeting to focus on the latest evidence for MRSA prevention and control measures and treatment in Rome, Italy, in March 2010. This review is based on the proceedings of that meeting.

In particular, this document outlines specifically the opinions expressed by experienced clinicians and scientists on the role of screening and decolonisation as useful tools in such management strategies. Low-prevalence countries were not considered a major issue: they have very similar screening policies. In our opinion, the target audience for this document should include health policy-makers, infection control teams, and clinicians working in hospitals with endemic MRSA, i.e. a situation where MRSA transmission rates are high and MRSA is constantly being circulated amongst the population present in the hospital and re-introduced by patients previously admitted to the same or other institutes in a locality/region where MRSA is endemic [7]. Indications for screening and decolonisation are not necessarily uniformly directed at every hospital within any given country. A recurrent and important feature since MRSA was first reported in the early 1960s has been that hospitals can vary in their MRSA rates, not just between countries but within a country or even in the same city [8], [9].

However, it is important to harmonise infection prevention and control measures between hospitals to limit MRSA spread between them, and a good example of such harmonisation is to ensure that hospitals inform one another when they transfer MRSA-affected patients between their institutions [10], [11], [12].

Screening involving the use of microbiological procedures to detect the carriage of MRSA by individuals without evidence of clinical infection is an essential ‘pillar’ of any MRSA control programme [13], [14], [15]. Since such procedures carry significant healthcare costs, it follows that any surveillance undertaken be of proven benefit to the overall strategies put in place for the prevention and control of MRSA infections. This is often difficult to ascertain, as such procedures are frequently multifaceted and analysing the contribution of any one component to observed outcomes can, in practice, be extremely difficult [16].

However, it was stressed that some sort of MRSA screening is essential in order to be successful in MRSA prevention and control. When considering the design of such a screening programme, it is essential to be aware of the context, specifically the MRSA occurrence levels nationally, regionally and locally. It is vital that nationally agreed guidance is incorporated into local policies and that relevant practices are audited regularly (this is also called process surveillance) to ensure that there is compliance. Policies may need to be modified locally based on the results of these audits so that they remain fit for purpose. This is especially pertinent given the changing landscape in Europe with the emergence of CA-MRSA and LA-MRSA.

Section snippets

Universal and targeted screening

‘Who’ should be screened for MRSA as well as ‘where’ and ‘when’ are still open questions. Several sites are recommended when screening patients. The anterior nares are the ‘headquarters’ of S. aureus/MRSA carriage and should always be included, although some data suggest that CA-MRSA may not be carried in the nose as frequently as other MRSA [4]. Data from community outbreaks suggest that skin-to-skin, and to a lesser extent skin-to-fomite, contacts represent common routes of transmission [17].

Screening after hospital discharge

Discharge/follow-up screening and decolonisation of specific patients may be appropriate to break the feedback loop of colonisation/infection that may occur when patients who remain colonised are re-admitted to hospital [42], [43]. Patients for whom there is considered to be a significant risk of acquiring MRSA during hospitalisation should be screened on discharge, and more so if they are expected to be re-admitted to hospital in the future, especially given that MRSA colonisation can be

Isolation and decolonisation

Once MRSA colonisation/infection is detected, contact isolation should be implemented to prevent cross-transmission. Physical isolation of patients found to be colonised with MRSA on admission into a separate unit has two key advantages: it establishes a physical barrier for transmission of MRSA between an MRSA-positive patient and other patients; and it highlights the precautions necessary for healthcare workers (HCWs) and visitors to follow [2], [7]. In an ideal world, all MRSA-positive

Staff screening

Staff screening is a complex consideration both microbiologically and in terms of employee care. There are various categories of screening that have been considered, including: anonymous staff screening whilst on duty to encourage improved hand hygiene or to increase awareness [57]; pre-employment and agency staff screening; screening to plan eradication regimen design; and screening to confirm MRSA eradication. Although potentially contentious, there is also ad hoc screening of staff whilst on

Environmental decolonisation

It has been demonstrated that the immediate environment around patients is often positive for MRSA. This is especially important in ICUs where much of the equipment will become contaminated with MRSA [60]. Routine disinfection of such equipment and potentially contaminated surfaces is therefore part of the MRSA control bundle of measures. Yet the importance of environmental cleaning as a single measure within an infection control programme has never been quantified. Environmental sources of

Ongoing European projects

MOSAR (Mastering Hospital Antimicrobial Resistance in Europe), a Europe-wide research network co-ordinated by INSERM (the French National Institute of Health and Medical Research) and supported by the European Commission, was established in 2007 and will examine factors determining the dynamics of spread of antimicrobial-resistant bacteria within healthcare facilities and the relative efficacy and medicoeconomic impact of control strategies. Currently, the MOSAR network has three clinical

Conclusions

As concluded in an earlier publication of a consensus statement by experienced practitioners in the field of prevention and control of healthcare-associated infections, including MRSA, “success in preventing and controlling MRSA is dependent on the appropriate attitude and high standards of professionalism amongst all who deliver healthcare”. To do this, appropriate evidence-based strategies are axiomatic. Standard precautions, especially hand hygiene, together with isolation/cohorting,

Acknowledgments

The meeting was sponsored by the following companies, which gave unrestricted education grants: Astellas Pharma; Becton Dickinson; bioMérieux; Cepheid; Novartis; and Wyeth. This review is based on the proceedings of an expert panel meeting jointly held by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC), 5–6 March 2010, Rome, Italy.

Funding: No funding sources.

Competing interests: None declared.

Ethical approval:

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