Methicillin-resistant Staphylococcus aureus in a Canadian intensive care unit: Delays in initiating effective therapy due to the low prevalence of infection.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) infection in intensive care units (ICUs) has increased dramatically in prevalence in recent years, and is associated with increased morbidity, mortality and cost of care. The aim of the present study was to describe the epidemiology and outcomes of MRSA infection in the general systems ICU at the University of Alberta Hospital in Edmonton, Alberta.
METHODS: A retrospective cohort analysis of patients infected with MRSA in a general systems ICU was conducted from January 1, 1997, to August 15, 2005.
RESULTS: Forty-six cases of MRSA were identified, of which 36 (78.3%) were infected. The most common admitting diagnoses included respiratory failure (41.7%) and sepsis or septic shock (36.1%). Infection was hospital acquired in 58.3% of cases (10 cases ICU acquired), with a median time to infection of 11 days. The most common sites of infection were the respiratory tract, skin and blood. Median lengths of stay were 13 days in the unit and 27 days in-hospital. Crude mortality was 55.6%. Time to appropriate antimicrobial treatment was delayed in 80.5% of patients. Four prototypical Canadian MRSA (CMRSA) strains were identified by pulsed-field gel electrophoresis. Hospital-acquired strains were predominantly CMRSA-2 (59%), indicating that this clone circulates at the University of Alberta Hospital.
CONCLUSIONS: MRSA infection remains uncommon at the University of Alberta Hospital, resulting in delays in instituting appropriate antimicrobial therapy. To date, only a few community-acquired strains have been noted. ICU acquisition of MRSA remains rare, with only 10 cases over the past nine years. The majority of hospital-acquired strains were CMRSA-2.