Isolation of patients in single rooms or cohorts to reduce spread of MRSA in intensive-care units: prospective two centre study

Summary

Background

Hospital-acquired infection due to meticillin-resistant Staphylococcus aureus (MRSA) is common within intensive-care units. Single room or cohort isolation of infected or colonised patients is used to reduce spread, but its benefit over and above other contact precautions is not known. We aimed to assess the effectiveness of moving versus not moving infected or colonised patients in intensive-care units to prevent transmission of MRSA.

Methods

We undertook a prospective 1-year study in the intensive-care units of two teaching hospitals. Admission and weekly screens were used to ascertain the incidence of MRSA colonisation. In the middle 6 months, MRSA positive patients were not moved to a single room or cohort nursed unless they were carrying other multiresistant or notifiable pathogens. Standard precautions were practised throughout. Hand hygiene was encouraged and compliance audited.

Findings

Patients' characteristics and MRSA acquisition rates were similar in the periods when patients were moved and not moved. The crude (unadjusted) Cox proportional-hazards model showed no evidence of increased transmission during the non-move phase (0·73 [95% CI 0·49–1·10], p=0·94 one-sided). There were no changes in transmission of any particular strain of MRSA nor in handwashing frequency between management phases.

Interpretation

Moving MRSA-positive patients into single rooms or cohorted bays does not reduce crossinfection. Because transfer and isolation of critically ill patients in single rooms carries potential risks, our findings suggest that re-evaluation of isolation policies is required in intensive-care units where MRSA is endemic, and that more effective means of preventing spread of MRSA in such settings need to be found.

Published online January 7, 2005 http://image.thelancet.com/extras/04art9304web.pdf

Introduction

Hospital-acquired infections—a fifth of which are caused by meticillin-resistant Staphylococcus aureus (MRSA)—are estimated to cost the UK National Health Service (NHS) £1 billion per year.¹ The incidence of MRSA is especially high within intensive-care units, with one in six patients in English units being colonised, infected, or both.² National guidelines for preventing the spread of MRSA recommend contact precautions and isolation of infected or colonised patients in a single room or cohort—ie, grouping them geographically with designated staff, though without the benefit of a physical barrier.3, 4, 5 Although workers on several reports have suggested a benefit from single-room isolation or cohort nursing, in a systematic review no well-designed studies were noted that allowed the role of isolation measures alone to be assessed.⁶ Such reports⁶ have been predominantly retrospective, lacking in proper statistical analysis, and generally undertaken in response to outbreaks rather than within intensive-care units of high endemicity. Moreover, isolation was generally introduced within a package of measures, variably including surveillance, improved handwashing compliance, reduction in ward activity, and addition of other treatments.⁶

The continuing rise in MRSA infection rates, the endemicity of MRSA in many countries, the inconsistency in current approach (eg, 24% of English intensive-care units do not isolate affected patients),² and the ongoing debate and scarcity of conclusive evidence on the use of infection control measures3, 7, 8 all raise important questions about the value of isolation strategies. The implications for resource use and, in particular, potential risks to the critically ill patient inherent in transfer and isolation7, 8, 9 mandate the need for definitive studies. We thus aimed to assess the benefit on MRSA transmission of isolation in single rooms or cohorts, over and above standard precautions.