Control of methicillin-resistant Staphylococcus aureus outbreak involving several hospitals.

This population-based, retrospective, cohort study describes a large methicillin-resistant Staphylococcus aureus (MRSA) epidemic caused by one strain (E1) in the greater Helsinki region. The epidemic comprised 210 cases at several hospitals, but was finally controlled. The study period ranged from June 1991 to December 2000. The epidemic peaked in 1993-1995 with 143 cases (68% of total cases). From August 1993, all MRSA-positive cases at the eight municipal hospitals were isolated and barrier nursed. Contacts were cohorted and screened for MRSA colonization. Decolonization treatment was administered to some chronic carriers. MRSA cases and contacts were identified in the joint patient register of the municipal hospitals from August 1993. The annual incidence of MRSA E1 in Helsinki City area per 100,000 inhabitants rose from 0.2 in 1991 to 13.6 in 1994. It decreased from 1995, reaching 0.7 per 100,000 in 2000. A jointly agreed policy on MRSA and timely co-operation between all units were essential for control of this epidemic.