Pathogenic Significance of Methicillin Resistance for Patients with Staphylococcus aureus Bacteremia

• Published in: Clinical infectious diseases Vol. 30; no. 2; pp. 368 - 373
• Main Authors: Soriano, A., Martínez, J. A., Mensa, J., Marco, F., Almela, M., Moreno-Martínez, A., Sánchez, F., Muñoz, I., Jiménez de Anta, M. T., Soriano, E.
• Format: Journal Article
• Language: English
• Published: Chicago, IL The University of Chicago Press 01-02-2000; University of Chicago Press
• Subjects: Adult; Aged; Analysis of Variance; Bacteremia; Bacteremia - drug therapy; Bacteremia - epidemiology; Bacterial diseases; Biological and medical sciences; Case-Control Studies; Clinical Articles; Cohort Studies; Confidence Intervals; Female; Hospital units; Human bacterial diseases; Humans; Incidence; Infections; Infectious diseases; Intensive care units; Logistic Models; Male; Medical sciences; Methicillin Resistance; Microbial Sensitivity Tests; Middle Aged; Mortality; Multivariate Analysis; Odds Ratio; Prognosis; Pulmonary heart disease; Risk Factors; Shock tests; Spain - epidemiology; Staphylococcal Infections - drug therapy; Staphylococcal Infections - epidemiology; Staphylococcal infections, streptococcal infections, pneumococcal infections; Staphylococcus aureus; Staphylococcus aureus - drug effects; Staphylococcus aureus - pathogenicity; Survival Analysis; Spain; Human; β-Lactams; Etiopathogenesis; Bacteremia; Meticillin; Result; Infection; Penicillin derivatives; Antibiotic; Cohort study; Bacteriosis; Bacteria; Micrococcales; Micrococcaceae; Antibacterial agent; Negative therapeutic reaction; Staphylococcus aureus
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1086/313650

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.