Development of a multilocus sequence typing scheme for intestinal spirochaetes within the genus Brachyspira T. Ra ˚ sba ¨ ck, 1,2 K.-E. Johansson, 1,3 D. S. Jansson, 2,4 C. Fellstro ¨m, 2 M. Y. Alikhani, 5,6 T. La, 6 D. S. Dunn 7 and D. J. Hampson 6 Correspondence T. Ra ˚ sba ¨ck therese.rasback@sva.se 1 Department of Bacteriology, National Veterinary Institute (SVA), SE-751 89 Uppsala, Sweden 2 Department of Clinical Sciences, Swedish University of Agricultural Sciences (SLU), PO Box 7018, SE-750 07 Uppsala, Sweden 3 Department of Biomedical Sciences and Veterinary Public Health, PO Box 7009, Swedish University of Agricultural Sciences (SLU), SE-750 07 Uppsala, Sweden 4 Department of Pigs, Poultry and Ruminants, National Veterinary Institute (SVA), SE-751 89 Uppsala, Sweden 5 Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran 6 School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch 6150, Australia 7 Centre for Comparative Genomics, Murdoch University, Murdoch 6150, Australia Received 29 March 2007 Revised 22 August 2007 Accepted 28 August 2007 The purpose of this study was to evaluate a multilocus sequence typing (MLST) scheme for intestinal spirochaetes of the genus Brachyspira. Eight loci mainly coding for enzymes previously used in multilocus enzyme electrophoresis analysis of Brachyspira species were examined in 66 Brachyspira field isolates and type/reference strains. The isolates and strains were recovered from pigs, birds, dogs and a mouse and originated from seven European countries, the USA and Canada. Forty-six isolates represented recognized Brachyspira species and 20 represented provisionally designated species or isolates that have not been classified. Only two loci gave PCR products for all 66 strains and isolates, but amplicons for seven loci were obtained for 44 of the isolates. Sequences for each locus had a DNA allelic variation of 30–47 and an amino acid allelic variation of 14–47 that gave rise to the same number of sequence and amino acid types (58) for the strains and isolates studied. A population snapshot based on sequence and amino acid types showed a close phylogenetic relationship amongst the porcine isolates from the same geographical regions, and indicated a close evolutionary relationship between isolates recovered from pigs and mallards. A general concordance was obtained between the MLST groupings and classifications based on culture and biochemical tests, 16S rDNA sequence analysis and random amplified polymorphic DNA analysis. This is a first step towards establishing an MLST system for use in identifying Brachyspira species and determining relationships between individual strains and species in the genus. INTRODUCTION The fastidious anaerobic intestinal spirochaetes of the genus Brachyspira (formerly Serpulina) are commonly found colonizing the large intestines of a wide range of animals, including humans (Hampson & Stanton, 1997; Duhamel, 2001). Currently there are seven officially named species in the genus, and several provisionally named species. Some species are important causes of enteric disease, particularly in pigs and poultry. Brachyspira hyodysenteriae is the cause of swine dysentery (Taylor & Alexander, 1971) and Brachyspira pilosicoli causes intestinal spirochaetosis in pigs and other species (Taylor et al., 1980; Duhamel, 2001). In poultry, B. pilosicoli, Brachyspira intermedia and Brachyspira alvinipulli cause reduced egg Abbreviations: AAT, amino acid type; MLEE, multilocus enzyme electrophoresis; MLST, multilocus sequence typing; RAPD, random amplified polymorphic DNA; ST, sequence type. The GenBank/EMBL/DDBJ accession numbers for the core sequences for the MLST loci used for B. hyodysenteriae strain WA1 and B. pilosicoli strain 95/1000 are EF488202–EF488215. Microbiology (2007), 153, 4074–4087 DOI 10.1099/mic.0.2007/008540-0 4074 2007/008540 G 2007 SGM Printed in Great Britain