Phylogenomic Analysis Reveals an Asian Origin for African Burkholderia pseudomallei and Further Supports Melioidosis Endemicity in Africa

Abstract

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.

Phylogeography ofBurkholderia pseudomalleiIsolates, Western Hemisphere

“…These studies indicate that Southeast Asia was the source of isolates from Africa, and Africa then became the source for B. pseudomallei in the Western Hemisphere, potentially associated with transfer to the Americas by the slave trade ( 10 , 11 ). Recent work has also shown the utility of SNP analysis in associating isolates of B. pseudomallei from patients with environmental isolates to establish epidemiologic links to better understand sources of infection ( 12 – 14 ).…”

“…Subsequent studies by Sarovich et al ( 10 ) and Chewapreecha et al ( 11 ) added support to this hypothesis by inferring relatedness from whole-genome SNPs. These studies indicate that Southeast Asia was the source of isolates from Africa, and Africa then became the source for B. pseudomallei in the Western Hemisphere, potentially associated with transfer to the Americas by the slave trade ( 10 , 11 ).…”

Loss of Methyltransferase Function and Increased Efflux Activity Leads to Doxycycline Resistance in Burkholderia pseudomallei

“…In the regions of northern Australia and Southeast Asia where melioidosis is endemic, infections caused by B. pseudomallei are a major cause of bacterial pneumonia and acute bacterial sepsis (1). Outside these known areas of endemicity, this bacterium has been sporadically identified in almost all tropical regions around the globe, with the full scale of its presence slowly being unmasked (2,3). A recent estimate of global mortality due to melioidosis, at 89,000 deaths per year, makes the potential burden of melioidosis comparable to that of measles (4).…”

A Burkholderia pseudomallei Infection Imported from Eritrea to Israel

“…However, because of low-grade resolution of the MLST typing method, high rates of horizontal gene transfer of the species, and potential ST homoplasy, a more discriminatory approach such as genome-wide single-nucleotide polymorphisms analysis is needed to determine the true relationship between strains. 11 Interestingly, recent phylogenomic analysis of a large B. pseudomallei strain collection strongly supports an ancient Asian origin for African organisms, which possibly crossed the ocean through human migration and trade, or were carried by migratory birds flying along the Asia-east Africa flyway. 11 The detection of an imported case of melioidosis in a country with well-resourced medical facilities revealed for the first time that the disease is endemic in the Horn of Africa, and the isolated organism appears to be only distantly related to B. pseudomallei strains from the western regions of the continent.…”

“…11 Interestingly, recent phylogenomic analysis of a large B. pseudomallei strain collection strongly supports an ancient Asian origin for African organisms, which possibly crossed the ocean through human migration and trade, or were carried by migratory birds flying along the Asia-east Africa flyway. 11 The detection of an imported case of melioidosis in a country with well-resourced medical facilities revealed for the first time that the disease is endemic in the Horn of Africa, and the isolated organism appears to be only distantly related to B. pseudomallei strains from the western regions of the continent. The epidemiological implications of the case are dual.…”