Clustering MRSA in Europe indicates diffusion through regional health-care networks

The study, published in PLoS Medicine, used an interactive Web tool to map different strains of the Staphylococcus aureus (S. aureus) bacterium across the continent.

MRSA infections have become more prevalent in hospitals over the past ten years, and information about its geographical distribution could help us to understand how it spreads and how to control it.

In 2006 Hajo Grundmann, of the University Medical Centre in Groningen in the Netherlands, and colleagues assembled a large group of collaborators in 450 European hospitals located in 26 different countries. These hospitals collected both MRSA and methicillin-sensitive S. aureus (MSSA) isolates from infected patients -- MRSA emerges when MSSA clones acquire resistance to antibiotics. National laboratories identified specific strains of S. aureus by molecular typing and entered this information into a Web-based mapping application which is publicly available (http://www.spatialepidemiology.net/srl-maps).

The results show that strains of MRSA tend to cluster within regional borders and, in several instances, were associated with individual hospitals. This suggests that MRSA is mainly spread by patients who are repeatedly admitted to different hospitals. "Control efforts aimed at interrupting the spread within and between health care institutions may not only be feasible but ultimately successful," conclude the researchers.

Franklin Lowy of Columbia University -- uninvolved in the research -- discusses the study in a Perspective and suggests that it "illustrates the ability of spatial mapping techniques to help understand the spread of new or re-emerging pathogens at the local as well as the international level''