title: Secular changes in incidence and mortality associated with Staphylococcus aureus bacteraemia in Quebec, Canada, 1991-2005.
abstract: In order to examine secular changes in the incidence and mortality associated with Staphylococcus aureus bacteraemia before and after the emergence of methicillin-resistant S. aureus (MRSA), a retrospective cohort study of 815 patients with S. aureus bacteraemia was performed in the Estrie region of Quebec, Canada, between 1991 and 2005. The primary outcome was all-cause 30-day mortality. Between 1991-1993 and 2003-2005, the proportion of cases attributed to endocarditis and pneumonia increased from 4% to 11% and from 2% to 11%, respectively, while that attributed to catheter infections decreased from 49% to 17%. MRSA was almost absent in 1991-1999, but accounted for 10% and 20% of cases in 2000-2002 and 2003-2005, respectively. The population incidence of bacteraemia caused by methicillin-susceptible S. aureus (MSSA) remained stable between 1997 and 2005, while that of MRSA increased from 0 to 7.4/100 000. Risk-factors for mortality included age, co-morbidities, female gender, residence outside the city of Sherbrooke, pneumonia (OR 3.35, 95% CI 1.96-5.73) or endocarditis (OR 2.89, 95% CI 1.67-5.01) as the source, and an absence of treatment. After adjusting for confounders, patients with MRSA bacteraemia had a higher mortality rate than those with MSSA bacteraemia (OR 2.21, 95% CI 0.99-4.96, p 0.053). Mortality in patients with MSSA bacteraemia was 19% (16/83) in 1991-1993, 23% (26/113) in 1994-1996, 29% (50/173) in 1997-1999, and 28% (52/185) in 2000-2002, decreasing to 15% (28/192) in 2003-2005, which impacted on the relative mortality rates of MRSA and MSSA. MRSA did not replace, but added to, an existing stable incidence of MSSA bacteraemia.
authors.affiliation: Department of Microbiology and Infectious Diseases, University of Sherbrooke, Quebec, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Allard
authors.forename: A
authors.initials: A
authors.lastname: Carignan
authors.forename: M
authors.initials: M
authors.lastname: Bergevin
authors.forename: I
authors.initials: I
authors.lastname: Boulais
authors.forename: V
authors.initials: V
authors.lastname: Tremblay
authors.forename: P
authors.initials: P
authors.lastname: Robichaud
authors.forename: R
authors.initials: R
authors.lastname: Duperval
authors.forename: J
authors.initials: J
authors.lastname: Pepin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016470:Bacteremia / Q000453:epidemiology* / Q000401:mortality*; D015331:Cohort Studies; D005260:Female; D006785:Hospitals, University; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D011792:Quebec / Q000453:epidemiology; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000401:mortality*