O33 – Predictors of Mortality Among Intravenous Drug Users with Staphylococcus aureus Bacteremia
Author(s):
Background: Staphylococcus aureus bacteremia (SAB) and its complications remain a persistent and challenging problem among intravenous drug users (IVDUs) that has resisted advances in medical and surgical therapies.
Hypothesis: We sought to determine the risk factors associated with mortality among IVDUs with SAB.
Methods: We retrospectively reviewed all patients admitted with SAB between 2008 and 2012 at a tertiary-care centre in Southwestern Ontario. Hospital records were used to identify IVDUs, admissions to the intensive care unit (ICU), complications of SAB such as infective endocarditis (IE) and osteomyelitis, and mortality. Multivariable logistic regression was performed to determine predictors of mortality in all SAB patients, and particularly in IVDUs. P values less than 0.05 were considered statistically significant.
Results: We identified 927 patients in our study: 167 (18%) were IVDUs. IVDUs were significantly younger than non-IVDUs (p< 0.0001), and had increased frequencies of IE (p< 0.0001), osteomyelitis (p< 0.0001), and sepsis (p= 0.022). Patients with IE were more likely to be infected by methicillin-sensitive, rather than methicillin-resistant, S. aureus (p= 0.0086). A similar proportion of IVDUs and non-IVDUs required ICU admission (23% and 30% respectively, p= 0.086). Although overall mortality in our study was 40%, we observed a significant (p= 0.019) decline in annual mortality. On multivariable analysis, sepsis (OR 1.83, 95% CI: 1.35-2.49, p< 0.0001) and mechanical ventilation (OR 3.46, 95% CI: 1.87-6.37, p< 0.0001) were independently associated with mortality among all patients with SAB. Among IVDUs, diagnosis of IE (OR 2.54, 95% CI: 1.13-5.68, p< 0.024) and prolonged (> 21 days) mechanical ventilation (OR 19.8, 95% CI: 3.74-104.8, p< 0.0001) were independent predictors of mortality. Methicillin resistance was not predictive of mortality in either population.
Conclusions: This study, to our knowledge, features the largest single-centre retrospective review of SAB in Canada. Identification of mortality predictors, combined with the characterization of antimicrobial resistance, may guide empiric therapy for patients with SAB, especially when there is clinical concern for complicated infections such as IE. This study also highlights the importance of reducing the duration of mechanical ventilation among patients with SAB, paving the way for future prospective studies.