Content:
ABSTRACT
Burkholderia pseudomallei
, an environmental bacterium that causes the deadly disease melioidosis, is endemic in northern Australia and Southeast Asia. An increasing number of melioidosis cases are being reported in other tropical regions, including Africa and the Indian Ocean islands.
B. pseudomallei
first emerged in Australia, with subsequent rare dissemination event(s) to Southeast Asia; however, its dispersal to other regions is not yet well understood. We used large-scale comparative genomics to investigate the origins of three
B. pseudomallei
isolates from Madagascar and two from Burkina Faso. Phylogenomic reconstruction demonstrates that these African
B. pseudomallei
isolates group into a single novel clade that resides within the more ancestral Asian clade. Intriguingly, South American strains reside within the African clade, suggesting more recent dissemination from West Africa to the Americas. Anthropogenic factors likely assisted in
B. pseudomallei
dissemination to Africa, possibly during migration of the Austronesian peoples from Indonesian Borneo to Madagascar ~2,000 years ago, with subsequent genetic diversity driven by mutation and recombination. Our study provides new insights into global patterns of
B. pseudomallei
dissemination and adds to the growing body of evidence of melioidosis endemicity in Africa. Our findings have important implications for melioidosis diagnosis and management in Africa.
IMPORTANCE
Sporadic melioidosis cases have been reported in the African mainland and Indian Ocean islands, but until recently, these regions were not considered areas where
B. pseudomallei
is endemic. Given the high mortality rate of melioidosis, it is crucial that this disease be recognized and suspected in all regions of endemicity. Previous work has shown that
B. pseudomallei
originated in Australia, with subsequent introduction into Asia; however, the precise origin of
B. pseudomallei
in other tropical regions remains poorly understood. Using whole-genome sequencing, we characterized
B. pseudomallei
isolates from Madagascar and Burkina Faso. Next, we compared these strains to a global collection of
B. pseudomallei
isolates to identify their evolutionary origins. We found that African
B. pseudomallei
strains likely originated from Asia and were closely related to South American strains, reflecting a relatively recent shared evolutionary history. We also identified substantial genetic diversity among African strains, suggesting long-term
B. pseudomallei
endemicity in this region.