Burkholderia pseudomallei Genotype Distribution in the Northern Territory, Australia

Chapple, Stephanie N. J.; Price, Erin P.; Sarovich, Derek S.; McRobb, Evan; Mayo, Mark; Kaestli, Mirjam; Spratt, Brian G.; Currie, Bart J.

doi:10.4269/ajtmh.15-0627

Cited by 19 publications

(28 citation statements)

References 21 publications

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“…Despite this, ST-36 and ST-109 comprised nearly 50% of the 135 isolates examined and ST-327 and ST-553 were the only additional molecular types for which we identified more than five isolates. These results are consistent with previous studies suggesting genetic diversity and abundance can vary amongst different B. pseudomallei STs and that there is an overrepresentation of a few STs within the Darwin region 6,9 . Five STs have been shown to comprise 90% of the overall clinical and environmental isolate abundance in Darwin and consistent with this, three of these were the most frequently identified molecular types in this study (ST-36, ST-109 and ST-553) 9 .…”

Section: Discussionsupporting

confidence: 93%

“…We also found significantly more ST-36 in soil compared to water, collectively suggesting that the ST is well-established in the urban Darwin environment and this may be why we observed no spatial clustering for the strain. Interestingly, while ST-109 is also one of the region's most frequently identified and widely dispersed molecular types, particularly in rural Darwin which was not included in this study, we observed a significant cluster within the city urban centre 6,9,17 . Since construction and earthwork projects have substantially increased in urban central Darwin in recent years, soil disturbance may have caused the strain to resurface and spread throughout the urban area.…”

Section: Discussionmentioning

confidence: 57%

“…Three of the four common STs examined as part of the study were highly localised in the urban Darwin environment. While we identified no spatial clustering of ST-36, it is one of the Darwin region's most frequently isolated molecular types and has been shown to be a significant source of melioidosis infection in the region since the Darwin Prospective Melioidosis Study (DPMS) began in 1989 5,6,9 . We also found significantly more ST-36 in soil compared to water, collectively suggesting that the ST is well-established in the urban Darwin environment and this may be why we observed no spatial clustering for the strain.…”

Section: Discussionmentioning

confidence: 74%

“…Previous phylogenetic investigations of B. pseudomallei have shown that Australian strains are ancestral to those found in Southeast Asia and globally, with the highest degree of genetic diversity identified in the Northern Territory of Australia 6,9,12,13 . Nevertheless, the nature and mechanisms for the global spread of B. pseudomallei remain to be elucidated, with explanations for autochthonous cases in the USA still proving elusive 33 .…”

Section: Discussionmentioning

confidence: 97%

“…Populations of B. pseudomallei are ecologically established and individual strain types are typically found less than 50 linear kilometres from one another in the environment 6,7,17 . Despite this, distinct genetic populations of the bacterium have only been documented across larger geographical boundaries, including the robust partitioning of Asian and Australian isolates at Wallace's Line 7,12,13,38 .…”

Section: Discussionmentioning

confidence: 99%

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Whole-genome sequencing of Burkholderia pseudomallei from an urban melioidosis hot spot reveals a fine-scale population structure and localised spatial clustering in the environment

Rachlin

Mayo

Webb

et al. 2020

Sci Rep

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Melioidosis is a severe disease caused by the environmental bacterium Burkholderia pseudomallei that affects both humans and animals throughout northern Australia, Southeast Asia and increasingly globally. While there is a considerable degree of genetic diversity amongst isolates, B. pseudomallei has a robust global biogeographic structure and genetic populations are spatially clustered in the environment. We examined the distribution and local spread of B. pseudomallei in Darwin, northern territory, Australia, which has the highest recorded urban incidence of melioidosis globally. We sampled soil and land runoff throughout the city centre and performed whole-genome sequencing (WGS) on B. pseudomallei isolates. By combining phylogenetic analyses, Bayesian clustering and spatial hot spot analysis our results demonstrate that some sequence types (STs) are widespread in the urban Darwin environment, while others are highly spatially clustered over a small geographic scale. this clustering matches the spatial distribution of clinical cases for one St. Results also demonstrate a greater overall isolate diversity recovered from drains compared to park soils, further supporting the role drains may play in dispersal of B. pseudomallei Sts in the environment. collectively, knowledge gained from this study will allow for better understanding of B. pseudomallei phylogeography and melioidosis source attribution, particularly on a local level. Burkholderia pseudomallei is an environmental Gram-negative bacillus and the causative agent of melioidosis, a potentially fatal infection of humans and animals 1. Regions of high B. pseudomallei endemicity predominantly include Southeast Asia and northern Australia, though the bacterium is also increasingly found in other tropical regions including the Indian subcontinent, Africa and the Americas 2. Melioidosis is typically considered noncommunicable with direct person-to-person transmission and zoonotic disease being remarkably rare 3,4. Nearly all B. pseudomallei infections are caused by a single direct exposure event to contaminated soil or surface water in the environment and individual cases of melioidosis are typically the result of infection by different strains of the bacterium 5. A limited geographic dispersal of B. pseudomallei strains has also been identified and the bacterium is now recognised as being ecologically established and spatially clustered in the environment 6-8. This is in spite of the frequent opportunities B. pseudomallei has to spread within the water table, via agricultural and migratory animals, or in transported soil 6,9-11. This restricted geographical distribution has resulted in distinct genetic populations of the bacterium, which are evident despite high levels of gene recombination and sequence type (ST)

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 57%