Figure 3

Neighbour-joining tree based upon concatenated sequences of MLST alleles from human S. aureus strains. MLST allele sequences representing each clinical strain studied here were used to generate a neighbour joining tree using MEGA 4. The A domain isotypes carried by strains of each MLST genotype, determined by sequencing and hybridization analysis, are indicated. The dashed line indicates the separation of the MLST genotypes into Groups 1 and 2, which is based on sequence data from MLST alleles and other unlinked loci [24]. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (500 replicates) are shown next to the branches [36, 37]. The phylogenetic tree was linearized assuming equal evolutionary rates in all lineages [37]. The evolutionary distances were computed using the Maximum Composite Likelihood method [34]. and are in the units of the number of base substitutions per site.