Background: While methicillin-resistant Staphylococcus aureus (MRSA) is increasing in prevalence globally, Sweden is still a low-prevalence country enabling studies on the natural MRSA spread in subpopulations unaffected by a surrounding highly infected population. Substance dependence and injection drug use have been risk factors for MRSA carriage and infection in other countries. In this retrospective, longitudinal register study, we investigated MRSA epidemiology 1997-2013 in opioid and amphetamine-dependent individuals, in comparison with alcohol-dependent subjects.
Methods: Data from the national Swedish in- and outpatients registers included 73,201 individuals from 1997, 1999, 2004, 2009 and 2013. We analyzed substance use disorder and demographic predictors for MRSA using generalized estimating equations.
Results: The main finding was that both opioid (adjusted odds ratio [AOR]=2.82; 95% confidence interval [CI]=2.16, 3.67) and amphetamine dependence (AOR=2.71; 95% CI=1.70, 4.16) were significantly associated with MRSA diagnosis compared with alcohol dependence, when adjusting for age, sex and year.
Conclusions: These findings are of value to understand the dynamics of MRSA epidemiology among substance dependent persons with presumably low socioeconomic status and potential injection drug use, and implicate repeated surveillance of MRSA among these patients.