Abdelbary, Mohamed M. H.3; Wittenberg, Anne4; Cuny, Christiane3; Layer, Franziska3; Kurt, Kevin3; Wieler, Lothar H.4; Walther, Birgit4; Skov, Robert5; Larsen, Jesper5; Hasman, Henrik2; Fitzgerald, J. Ross6; Smith, Tara C.7; Wagenaar, J. A.8; Pantosti, Annalisa14; Hallin, Marie10; Struelens, Marc J.11; Edwards, Giles12; Boese, R.13; Nuebel, Ulrich3; Witte, Wolfgang3
1 National Food Institute, Technical University of Denmark2 Division of Epidemiology and Microbial Genomics, National Food Institute, Technical University of Denmark3 Robert Koch Institute4 Free University of Berlin5 Statens Serum Institut6 University of Edinburgh7 University of Iowa8 Utrecht University9 Istituto Superiore di Sanita10 Université Libre de Bruxelles11 European Centre for Disease Prevention and Control12 Scottish MRSA Reference Laboratory (SMRSARL)13 Labor Dr. Böse GmbH14 Istituto Superiore di Sanita
In the early 2000s, a particular MRSA clonal complex (CC398) was found mainly in pigs and pig farmers in Europe. Since then, CC398 has been detected among a wide variety of animal species worldwide. We investigated the population structure of CC398 through mutation discovery at 97 genetic housekeeping loci, which are distributed along the CC398 chromosome within 195 CC398 isolates, collected from various countries and host species, including humans. Most of the isolates in this collection were received from collaborating microbiologists, who had preserved them over years. We discovered 96 bi-allelic polymorphisms, and phylogenetic analyses revealed that an epidemic sub-clone within CC398 (dubbed 'clade (C)') has spread within and between equine hospitals, where it causes nosocomial infections in horses and colonises the personnel. While clade (C) was strongly associated with S. aureus from horses in veterinary-care settings (p = 2x10(-7)), it remained extremely rare among S. aureus isolates from human infections.