European Chlamydia abortus livestock isolate genomes reveal unusual stability and limited diversity, reflected in geographical signatures by Seth-Smith, HMB, Busó, LS, Livingstone, M, Sait, M, Harris, SR, Aitchison, KD, Vretou, E, Siarkou, VI, Laroucau, K, Sachse, K, Longbottom, D, Thomson, NR