Epidemiology and spa-type diversity of meticillin-resistant Staphylococcus aureus in community and healthcare settings in Norway

Background: There has been a marked increase in the incidence of meticillin-resistant Staphylococcus aureus (MRSA) during the past decade in Norway; a country with one of the lowest prevalence rates and an active 'search-and-destroy' policy applied to hospital settings. Aim: To characterize the trends of notification rates of community-associated (CA) and healthcare-associated (HA) MRSA in Norway, and explore the diversity and circulation of MRSA spa types within and outside healthcare settings. Methods: A registry-based study on notified MRSA infections and colonizations was conducted in Norway between 2006 and 2015. The diversity and abundance of CA- and HA-MRSA spa types were compared using novel ecological diversity measures (Hill numbers). Findings: During the study period, the monthly notification rate increased 6.9-fold and 1.8-fold among CA- and HA-MRSA, respectively; the increase was steeper among colonizations than infections. In both settings, the distribution of spa types was uneven, with a few dominant spa types and many singletons. The spa-type diversity of CA-MRSA was higher than HA-MRSA in terms of different types (685 vs 481), and increased during the study period. However, the diversity associated with the dominant spa types was similar and remained stable. A high overlap of spa types was estimated between the settings; spat002, t019 and t008 were the most common. Conclusion: The present findings suggest a strong connection between CA- and HA-MRSA epidemiology in Norway. If the fast-growing trend of CA-MRSA continues in the years to come, it may challenge current guidelines and infection control of MRSA in healthcare environments. (C) 2018 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.