Genetic diversity and recombination.

aNumber of isolates. bNumber of ST. cNumber of segregating sites. dNucleotide diversity using unique STs. eStandardized index of association. Only unique STs were used to avoid the effect of biased sample collections. Null hypothesis of panmixia (IAS = 0) is tested against significant linkage disequilibrium (IAS>0). *P<0.001. fThe value in parentheses is based on analysis of using six loci (excluding a highly polymorphic locus glnA).