Staphylococcus aureus bacteraemia in Gauteng academic hospitals, South Africa

Abstract

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) infections are responsible for longer hospital stays, increased hospital costs, and poorer outcomes compared to methicillin-sensitive S. aureus (MSSA) infections. We aimed to describe the epidemiology of S. aureus bacteraemia (SAB) and to determine factors associated with MRSA infection in South Africa. Methods: Cases of SAB were reported from September 2012 to September 2013 from three sentinel sites. A case was defined as the isolation of S. aureus from a blood culture during a 21-day period. Detailed clinical information was collected. Multivariable logistic regression was done to determine factors associated with MRSA infection and mortality. Results: There were 442 cases of SAB reported; antimicrobial susceptibility testing was performed on 240 isolates (54%). Thirty-six percent (86/240) of cases had an MRSA infection. A longer hospital stay before positive specimen collection (odds ratio (OR) 1.08, 95% confidence interval (CI) 1.02–1.13, p = 0.004), hospitalization in the last year (OR 15.7, 95% CI 2.5–99.5, p = 0.003), HIV infection (OR 4.9, 95% CI 1.05–22.90, p = 0.044), and antibiotic use in the previous 2 months (OR 0.1, 95% CI 0.01–0.68, p = 0.022) were independent predictors of MRSA. Older age, and in particular age 25–44 years (OR 22.2, 95% CI 2.7–185.5, p = 0.004, compared to those aged < 5 years), was the only independent predictor of mortality amongst cases with SAB. MRSA isolates were non-susceptible to more antimicrobial agents compared to MSSA isolates. Conclusions: HIV infection was an independent risk factor for MRSA infection. The selection of appropriate empirical antimicrobial treatment is essential in patients with MRSA infections because of non-susceptibility to many other antimicrobial classes.

Keywords

• Staphylococcus aureus
• Bacteraemia
• Methicillin-resistant
• HIV infection
• Mortality