Genetic diversity of Burkholderia pseudomallei isolates in Australia

Abstract

Melioidosis is caused by the gram-negative saprophytic bacterium Burkholderia pseudomallei, which is endemic to southeast Asia and northern Australia. We have previously found evidence of geographic localization of strains based on multilocus sequence typing (MLST). In this study, we examined the diversity of 277 isolates from northern Australia, which were resolved into 159 different sequence types. No sequence types were common to both Queensland and the Northern Territory, and there was significant differentiation between the alleles present in the two regions. The considerable diversity in sequence types contrasts with the limited diversity of alleles at MLST loci, supporting previous work suggesting a high rate of recombination relative to mutation in B. pseudomallei, where new sequence types are primarily generated by reassortment of existing alleles.

FIG. 1.

Map of northern Australia, showing locations of major towns and regions in the Northern Territory and Queensland.

FIG. 2.

eBURST diagram of ST from isolates in the present study, demonstrating STs found only on islands (green) only on the mainland (black) or both islands and the mainland (cyan). The size of the dots represents the relative frequency of the ST.

FIG. 3.

Bootstrap consensus tree based on the concatenated sequence at all loci demonstrating relatedness of Queensland (blue), Northern Territory (red), and island isolates (hollow).