The tree was constructed using concatenated DNA sequences obtained from the seven MLST loci (pgm, adh, alp, est, glpK, gdh and thi: 4,071 nucleotides). Bootstrap values are shown for stable nodes. The scale bar shows the distance equivalent to three substitutions per 1,000 nucleotide positions. The three major groups of descent are marked in different colours. ST8, ST52 and ST54 have been previously described , .