title: Pathogenic significance of methicillin resistance for patients with Staphylococcus aureus bacteremia.
abstract: To assess whether methicillin resistance is a microbial characteristic associated with deleterious clinical outcome, we performed a cohort study on 908 consecutive episodes of Staphylococcus aureus bacteremia and a case-control study involving 163 pairs of patients matched for preexisting comorbidities, prognosis of the underlying disease, length of hospitalization, and age. Of 908 bacteremic episodes, 225 (24.8%) were due to methicillin-resistant S. aureus (MRSA). Multivariate analysis did not reveal that methicillin resistance was an independent predictor for mortality when shock, source of bacteremia, presence of an ultimately or rapidly fatal underlying disease, acquisition of the infection in an intensive care unit (ICU), inappropriate empirical therapy, female sex, and age were taken into account. Nonetheless, methicillin resistance was an independent predictor for shock. The case-control study could not confirm that shock was linked to MRSA when prior antimicrobial therapy, inappropriate treatment, ICU residence, and female sex were considered. Our data suggest that cohort studies tend to magnify the relationship of MRSA with clinical markers of microbial pathogenicity and that this effect is a shortcoming of these kind of studies that is caused by inadequate control for underlying diseases.
authors.affiliation: Infectious Diseases Unit, Hospital Clinic, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Soriano
authors.forename: J A
authors.initials: JA
authors.lastname: Martínez
authors.forename: J
authors.initials: J
authors.lastname: Mensa
authors.forename: F
authors.initials: F
authors.lastname: Marco
authors.forename: M
authors.initials: M
authors.lastname: Almela
authors.forename: A
authors.initials: A
authors.lastname: Moreno-Martínez
authors.forename: F
authors.initials: F
authors.lastname: Sánchez
authors.forename: I
authors.initials: I
authors.lastname: Muñoz
authors.forename: M T
authors.initials: MT
authors.lastname: Jiménez de Anta
authors.forename: E
authors.initials: E
authors.lastname: Soriano
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016470:Bacteremia / Q000188:drug therapy / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000472:pathogenicity*; D016019:Survival Analysis