Evolutionary relationships of fnbA N1, N2 and N3 allele sequences. fnbA gene segments encoding the entire FnBPA A domain were sequenced from 14 isolates from divserse MLST genotypes. Strain P1 (ST-973)fnbA was sequenced previously . In addition, the fnbA gene sequences from MSSA 476 (ST-1); N315 (ST-5); MRSA252 (ST-36); COL (ST-250); RF122 (ST-151) as well as the archetype fnbA sequence from 8325-4 (ST-8) were included. The evolutionary history was inferred using the Neighbor-Joining method . Neighbour-joining trees were constructed using fnbA DNA sequences encoding the sub-domains N1 (a), N2 (b) and N3 (c) using MEGA 3. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (500 replicates) are shown next to the branches . The phylogenetic tree was linearized assuming equal evolutionary rates in all lineages . The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site.