Clustering of MRSA strains across Europe
Staphylococcus aureus is the main cause of purulent infection in humans. S. aureus has the potential for local as well as disseminated infection and can cause lesions in all tissues and anatomical sites. Infections can be either acquired in the community or in association with health care. The position of S. aureus as one of the most important human pathogens is largely due to its virulence potential and ubiquitous occurrence as a coloniser in humans, domestic animals, and livestock. Between 25% and 35% of healthy human individuals carry S. aureus on the skin or mucous membranes. Any injury that compromises epithelial integrity, trauma, medical or surgical interventions, as well as viral infections, can lead to tissue invasion. It is assumed that severity and outcome depend largely on the virulence of the introduced strain and the immune repertoire of the host. Occasionally, S. aureus acquires enhanced virulence and antimicrobial resistance through horizontal DNA transfer and maintains these mobile genetic elements in a predominantly clonal genomic background. Thus, clones of S. aureus are relatively stable and mainly diversify by the accumulation of single nucleotide substitutions in the absence of frequent interstrain recombination. It is therefore possible to discern different clones and clonal lineages by molecular typing. This method allows several important observations to be made regarding the evolution, epidemiology, and spread of clones with particular public health importance, such as hospital-, community- , and livestock-associated methicillin-resistant S. aureus (MRSA).
A new study finds that methicillin-resistant S. aureus (MRSA), responsible for several difficult-to-treat infections including blood poisoning and pneumonia and a particular problem in hospitals, occurs in distinct geographical clusters across Europe, indicating that MRSA is being diffused by patients moving between hospitals rather than spreading freely in the community. The study used an interactive Web tool to map different strains of the Staphylococcus 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.
Since 2006 a large group of collaborators in 450 European hospitals located in 26 different countries collected both MRSA and methicillin-sensitive S. aureus (MSSA) isolates from infected patients. 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. 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.
Geographic Distribution of Staphylococcus aureus Causing Invasive Infections in Europe: A Molecular-Epidemiological Analysis. PLoS Med 7(1): e1000215 doi:10.1371/journal.pmed.1000215:
Staphylococcus aureus is one of the most important human pathogens and methicillin-resistant variants (MRSAs) are a major cause of hospital and community-acquired infection. We aimed to map the geographic distribution of the dominant clones that cause invasive infections in Europe. In each country, staphylococcal reference laboratories secured the participation of a sufficient number of hospital laboratories to achieve national geo-demographic representation. Participating laboratories collected successive methicillin-susceptible (MSSA) and MRSA isolates from patients with invasive S. aureus infection using an agreed protocol. All isolates were sent to the respective national reference laboratories and characterised by quality-controlled sequence typing of the variable region of the staphylococcal spa gene (spa typing), and data were uploaded to a central database. Relevant genetic and phenotypic information was assembled for interactive interrogation by a purpose-built Web-based mapping application. Between September 2006 and February 2007, 357 laboratories serving 450 hospitals in 26 countries collected 2,890 MSSA and MRSA isolates from patients with invasive S. aureus infection. A wide geographical distribution of spa types was found with some prevalent in all European countries. MSSA were more diverse than MRSA. Genetic diversity of MRSA differed considerably between countries with dominant MRSA spa types forming distinctive geographical clusters. We provide evidence that a network approach consisting of decentralised typing and visualisation of aggregated data using an interactive mapping tool can provide important information on the dynamics of MRSA populations such as early signalling of emerging strains, cross border spread, and importation by travel. In contrast to MSSA, MRSA spa types have a predominantly regional distribution in Europe. This finding is indicative of the selection and spread of a limited number of clones within health care networks, suggesting that control efforts aimed at interrupting the spread within and between health care institutions may not only be feasible but ultimately successful and should therefore be strongly encouraged.
Related:
- MRSA: Methicillin-resistant Staphylococcus aureus
- Staphylococcus aureus: superbug
- Evolution and pathogenesis of Staphylococcus aureus
Tags: Antibiotics, Bacteria, Biology, Emerging disease, Health, Medicine, Microbiology, MRSA, Science
