Table 2. Indices of association for combinations of MLST alleles with and without tonB, and measurements of diversity conferred by individual loci indicate that tonB is highly diverse and likely subjected to horizontal gene transfer.
| Targets | IA |
| All MLST loci | 0.1112 |
| All loci excluding tonB | 0.1279 |
| phoE, gapA, tonB, infB | 0.0852 |
| gapA, tonB, infB, mdh | 0.1002 |
| tonB, infB, mdh, rpoB | 0.1017 |
| infB, mdh, rpoB, pgi | 0.1346 |
| phoE, gapA, rpoB, pgi | 0.1260 |