According to researchers from the University College London Hospitals, the Health Protection Agency and Royal Free Hampstead NHS Trust, all in London, minimizing the spread of methicillin-resistant Staphylococcus aureus (MRSA) within an intensive care unit (ICU) requires hand hygiene and effective routine environmental cleaning.

In a presentation at the International Conference on Prevention & Infection Control (ICPIC) held in Geneva, Switzerland, researchers explained that variability in MRSA policies and procedures reflects a need for more information regarding the relative contribution and clinical importance of the different modes of MRSA transmission.

A prospective one-year study was conducted within the ICU of two UK hospitals. Conventional sampling techniques were used to recover MRSA from the air and from high-contact sites located within the ward environment. All patients were screened for MRSA on admission and weekly during their stays. Samples from other sites were cultured when clinically indicated. MRSA was considered nosocomially acquired if detected more than 48 hours after admission. Possible transmission routes from donor to recipient via the hands of staff, the air or environmental surfaces were identified. Focused molecular typing via PFGE was used to explore these pathway hypotheses.

There were 2,654 admissions. 175 patients were positive for MRSA on admission while 78 acquired MRSA during their stay. MRSA was isolated from 208 of 18,596 surfaces, from 56 of 859 air samples and from the hands of staff on 59 of 4191 sampling occasions. 28 acquisition events occurred in ICU A. Only those involving an unusual PFGE pulsotype (i.e. one not recognized as being common and widespread within the UK hospital environment) were selected for further study. The likely source of nine colonizations was identified and of the tested hypotheses, seven implicated poor hand hygiene,  four inadequate cleaning and one airborne transmission. In ICU B, a higher level of endogenous and/or endemic MRSA meant evidence for patient-patient cross-transmission was more limited.

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