Emergence of Burkholderia pseudomallei Sequence Type 562, Northern Australia

Area of Science:

• Microbiology
• Genomics
• Epidemiology

Background:

• Burkholderia pseudomallei sequence type 562 (ST562) has expanded its range in northern Australia since 2005.
• This bacterium caused 61 human and 3 animal melioidosis cases between 2005 and 2019.
• ST562 cases initially clustered around a creek before spreading throughout urban Darwin and a nearby island.

Purpose of the Study:

• To investigate the expansion and genomic epidemiology of Burkholderia pseudomallei ST562 in northern Australia.
• To determine the origin and introduction dynamics of ST562 into the Darwin region.
• To analyze the genetic relatedness of Australian ST562 strains to international isolates.

Main Methods:

• Epidemiological analysis of melioidosis cases linked to ST562.
• Genomic analysis of ST562 isolates from Australia, China, and Taiwan.
• Temporal genomic analysis to estimate introduction dates.

Main Results:

• ST562 caused 12% of melioidosis cases in urban Darwin, with this proportion increasing over time.
• Genomic analysis revealed distant relationships between Australian ST562 strains and those from China and Taiwan.
• Temporal analysis suggested a single introduction of ST562 into the Darwin region around 1988.

Conclusions:

• Burkholderia pseudomallei ST562 has significantly expanded its presence and impact in northern Australia.
• The genetic data points to a single introduction event into Australia, likely around 1988.
• The precise origin and transmission pathway of ST562 into Australia remain undetermined.