Admission Screening of Methicillin-Resistant Staphylococcus aureus with Rapid Molecular Detection in Intensive Care Unit: A Three-Year Single-Centre Experience in Hong Kong

Background. The admission screening of methicillin-resistant Staphylococcus aureus (MRSA) by rapid molecular assay is considered to be an effective method in reducing the transmission of MRSA in intensive care unit (ICU). Method. The admission screening on patients from ICU once on their admissions by BD GeneOhm MRSA assay has been introduced to Prince of Wales Hospital, Hong Kong, since 2008. The assay was performed on weekdays and reported on the day of testing. Patients pending for results were under standard precautions until the negative screening results were notified, while contact precautions were implemented for MRSA-positive patients. In this study, we compared the MRSA transmission rate in molecular screening periods (2008 to 2010) with the historical culture periods (2006 to 2007) as control. Results. A total of 4679 samples were tested; the average carriage rate of MRSA on admission was 4.45%. By comparing with the historical culture periods, the mean incidence ICU-acquired MRSA infection was reduced from 3.67 to 1.73 per 1000 patient bed days. Conclusion. The implementation of admission screening of MRSA with molecular method in intensive care unit could reduce the MRSA transmission, especially in the area with high MRSA prevalence situation in Hong Kong. 1. Introduction Methicillin-resistant strain S. aureus (MRSA) is a major cause of nosocomial infections; it causes infections with clinical manifestations ranging from pustules to sepsis and even death [1]. MRSA is frequently encountered in health-care settings and represents over 50% of isolates from hospital-acquired S. aureus in some North American hospitals [2]. Most transmissions occur through the contaminated hands of healthcare workers in hospital settings. Early screening of patients for MRSA nasal carriage is an effective infection control strategy to identify those patients that require isolation. However, the utility of active surveillance screening has been evaluated in many studies, and its effectiveness is still controversial [3, 4]. This controversy may be attributed to the slow turnaround time of the conventional culture method. Recently, many commercial available molecular assays have been developed; they provide a rapid tool for laboratory to shorten the turnaround time of the screening and reduce the time for resolution of MRSA carrier status within a day. Currently, the evidence in supporting MRSA universal screening on admission by molecular method is mixed and inconclusive. In fact, the effectiveness of screening depends on the prevalence of MRSA, the resources