[An outbreak of MRSA in a nursing home in Oslo]

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) represent an increasing problem in Norway, also in nursing homes and other institutions for long-term care. We describe an outbreak of MRSA in a nursing home in Oslo 2004-5.

The nursing home has six wards with 185 beds. The building is old, all rooms have toilets and sinks, but showers are shared. Standard screening procedures were carried out according to the national MRSA guide and by using the nursing home's infection control programme. Later on we used more extensive screening of staff and patients.

The outbreak started in a ward for short-term care, but spread to a ward for patients with dementia after some months. Ten patients, seven staff members and two relatives of infected persons were diagnosed with MRSA. All bacteria probably belonged to the same strain. Four staff members and five patients who were infected had pre-existing wounds or eczema. The nursing home was declared free of MRSA 20 months after the outbreak started, but one member of staff remained a carrier for two years, and one patient became a chronic carrier of MRSA. During the first six months, infected patients were restricted to their rooms, and standard eradication procedures were carried out for five days. Later on, we introduced cohort isolation for infected, exposed and recently treated patients, a different screening routine, a prolonged eradication procedure, restrictions on staff working elsewhere and more stringent precautions for visitors.

An old building and insufficient isolation procedures during the first phase of the outbreak contributed to spreading MRSA and prolonging the outbreak. Cohort isolation seemed to be the most important measure to control the outbreak. All nursing homes should have a designated single patient room for contact precautions. Long-term carriers of MRSA in nursing homes represent a big challenge.