Molecular Phylogeny of Burkholderia pseudomallei from a Remote Region of Papua New Guinea

Abstract

BackgroundThe island of New Guinea is located midway between the world's two major melioidosis endemic regions of Australia and Southeast Asia. Previous studies in Papua New Guinea have demonstrated autochthonous melioidosis in Balimo, Western province. In contrast to other regions of endemicity, isolates recovered from both environmental and clinical sources demonstrate narrow genetic diversity over large spatial and temporal scales.Methodology/Principal FindingsWe employed molecular typing techniques to determine the phylogenetic relationships of these isolates to each other and to others worldwide to aid in understanding the origins of the Papua New Guinean isolates. Multi-locus sequence typing of the 39 isolates resolved three unique sequence types. Phylogenetic reconstruction and Structure analysis determined that all isolates were genetically closer to those from Australia than those from Southeast Asia. Gene cluster analysis however, identified a Yersinia-like fimbrial gene cluster predominantly found among Burkholderia pseudomallei derived from Southeast Asia. Higher resolution VNTR typing and phylogenetic reconstruction of the Balimo isolates resolved 24 genotypes with long branch lengths. These findings are congruent with long term persistence in the region and a high level of environmental stability.Conclusions/SignificanceGiven that anthropogenic influence has been hypothesized as a mechanism for the dispersal of B. pseudomallei, these findings correlate with limited movement of the indigenous people in the region. The palaeogeographical and anthropogenic history of Australasia and the results from this study indicate that New Guinea is an important region for the further study of B. pseudomallei origins and dissemination.

Burkholderia pseudomallei Isolates from Sarawak, Malaysian Borneo, Are Predominantly Susceptible to Aminoglycosides and Macrolides

“…This ruggedness is especially true in the central region, where ST881 and ST997 were isolated. The apparent geographic restriction associated with limited sequence diversity of ST881 is similar to previous reports of B. pseudomallei isolates from Papua New Guinea, where low diversity of B. pseudomallei was observed in a geographically isolated region of Western Province (24,25). The narrow genetic variability within the majority of the Sarawak isolates and those from Papua New Guinea could potentially reflect recent but independent introduction events in those two locations.…”

“…The narrow genetic variability within the majority of the Sarawak isolates and those from Papua New Guinea could potentially reflect recent but independent introduction events in those two locations. More likely, however, the observed overlap of certain STs in Malaysian Borneo with other Asian regions supports the hypothesis of a more ancient dispersal of B. pseudomallei to Malaysian Borneo, with dispersal and diversity in Sarawak restricted by its remoteness, and potentially also by limited anthropogenic activities (25).…”

Multilocus sequence typing of 102 Burkholderia pseudomallei strains isolated from China

“…The prevailing view of workers in the field is that strain lineages of B. pseudomallei possibly originated from Australia and subsequently spread to Southeast Asia and other regions [2,14]. Our results only suggest a link between B. pseudomallei from Thailand and China (Figs 3 and 4) but apart from ST562, no other ST was shared between strains from China and Australia.…”

Biogeography of Burkholderia pseudomallei in the Torres Strait Islands of Northern Australia

“…Moreover, a lateral gene transfer event in the evolutionary history of B. pseudomallei has been identified which broadly conforms to these expectations; Australian isolates are more likely to encode the ancestral B. thailandensis-like flagellum and chemotaxis gene cluster (BTFC) while isolates from Asia almost exclusively carry a Yersinia-like fimbrial gene cluster (YLF) (13). We recently reported that isolates of B. pseudomallei from the Western Province of Papua New Guinea (PNG) are not only distinct by MLST but also demonstrate a narrow genetic diversity in contrast to isolates from mainland Australia (14), most likely resulting from longterm geographical separation. Together, these studies have indicated that B. pseudomallei dispersal occurs with relative ease over terra firma yet is hampered by relatively narrow passages of seawater, findings that mirror observations of macro flora and fauna.…”