What drives the occurrence of the melioidosis bacterium Burkholderia pseudomallei in domestic gardens?

PLoS Negl Trop Dis. 2015 Mar 24;9(3):e0003635. doi: 10.1371/journal.pntd.0003635. eCollection 2015 Mar.

Abstract

Melioidosis is an often fatal infectious disease affecting humans and animals in tropical regions and is caused by the saprophytic environmental bacterium Burkholderia pseudomallei. Domestic gardens are not only a common source of exposure to soil and thus to B. pseudomallei, but they also have been found to contain more B. pseudomallei than other environments. In this study we addressed whether anthropogenic manipulations common to gardens such as irrigation or fertilizers change the occurrence of B. pseudomallei. We conducted a soil microcosm experiment with a range of fertilizers and soil types as well as a longitudinal interventional study over three years on an experimental fertilized field site in an area naturally positive for B. pseudomallei. Irrigation was the only consistent treatment to increase B. pseudomallei occurrence over time. The effects of fertilizers upon these bacteria depended on soil texture, physicochemical soil properties and biotic factors. Nitrates and urea increased B. pseudomallei load in sand while phosphates had a positive effect in clay. The high buffering and cation exchange capacities of organic material found in a commercial potting mix led to a marked increase in soil salinity with no survival of B. pseudomallei after four weeks in the potting mix sampled. Imported grasses were also associated with B. pseudomallei occurrence in a multivariate model. With increasing population density in endemic areas these findings inform the identification of areas in the anthropogenic environment with increased risk of exposure to B. pseudomallei.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agricultural Irrigation
  • Agriculture
  • Animals
  • Burkholderia pseudomallei / growth & development*
  • Fertilizers*
  • Humans
  • Melioidosis / microbiology
  • Nitrates
  • Phosphates
  • Poaceae / microbiology
  • Population Density
  • Salinity
  • Soil / chemistry*
  • Soil Microbiology*
  • Urea

Substances

  • Fertilizers
  • Nitrates
  • Phosphates
  • Soil
  • Urea

Grants and funding

This work was supported by grants from the Australian Research Council (www.arc.gov.au)(grant number LP110100691) and the Australian National Health and Medical Research Council (www.nhmrc.gov.au)(grant number 1046812). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.