Out of the ground: aerial and exotic habitats of the melioidosis bacterium Burkholderia pseudomallei in grasses in Australia.

Melioidosis is an emerging infectious disease of humans and animals in the tropics caused by the soil bacterium Burkholderia pseudomallei. Despite high fatality rates, the ecology of B.pseudomallei remains unclear. We used a combination of field and laboratory studies to investigate B.pseudomallei colonization of native and exotic grasses in northern Australia. Multivariable and spatial analyses were performed to determine significant predictors for B.pseudomallei occurrence in plants and soil collected longitudinally from field sites. In plant inoculation experiments, the impact of B.pseudomallei upon these grasses was studied and the bacterial load semi-quantified. Fluorescence in situ hybridization and confocal laser scanning microscopy were performed to localize the bacteria in plants. Burkholderia pseudomallei was found to inhabit not only the rhizosphere and roots but also aerial parts of specific grasses. This raises questions about the potential spread of B.pseudomallei by grazing animals whose droppings were found to be positive for these bacteria. In particular, B.pseudomallei readily colonized exotic grasses introduced to Australia for pasture. The ongoing spread of these introduced grasses creates new habitats suitable for B.pseudomallei survival and may be an important factor in the evolving epidemiology of melioidosis seen both in northern Australia and elsewhere globally.

Applications of Optical Neuroimaging in Usability Research.

In this article we review recent and potential applications of optical neuroimaging to human factors and usability research. We focus specifically on functional near-infrared spectroscopy (fNIRS) because of its cost-effectiveness and ease of implementation. Researchers have used fNIRS to assess a range of psychological phenomena relevant to human factors, such as cognitive workload, attention, motor activity, and more. It offers the opportunity to measure hemodynamic correlates of mental activity during task completion in human factors and usability studies. We also consider some limitations and future research directions.

The association of melioidosis with climatic factors in Darwin, Australia: A 23-year time-series analysis.

OBJECTIVES: Melioidosis is an often fatal disease in humans and animals and endemic in Southeast Asia and northern Australia. It is caused by the environmental bacterium Burkholderia pseudomallei. We analysed weather and climate factors preceding new melioidosis cases in Darwin and compared the time between weather event and admission to hospital for severe and average wet season rainfall. METHODS: In a time-series analysis from 1990 to 2013 we applied a boosted regression tree and a negative binomial model to investigate the association between melioidosis cases and weather events. Fitted Fourier terms controlled for long-term seasonal trends. RESULTS: We found a rise in the dew point, cloud cover, rainfall, maximum temperature and groundwater to be associated with an increased risk to acquire melioidosis. A shorter 'putative' incubation period was evident after severe rainfall events. Rainfall occurring early in the wet season was linked to more cases as was an increase in the local sea surface temperature reflecting local weather dynamics and precipitation. CONCLUSIONS: Our findings demonstrate a statistical association between frequency of recorded melioidosis cases and the nature and timing of rainfall related events and suggest a future rise in the sea surface and ambient temperature may lead to increased melioidosis.

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

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.

Melioidosis as a consequence of sporting activity.

In the tropical city of Darwin, Northern Territory, Australia, dry season soil sampling cultured Burkholderia pseudomallei from 7 (70%) of 10 sports fields. However, during the 23 years of the Darwin Prospective Melioidosis Study, only 5 (0.6%) of 785 melioidosis cases have been attributed to infection from sports fields. In one soccer player with cutaneous melioidosis, B. pseudomallei cultured from the player was identical by multilocus sequence typing and multilocus variable-number tandem repeat analysis with an isolate recovered from soil at the location on the sports field where he was injured. Melioidosis is uncommon in otherwise healthy sports persons in melioidosis-endemic regions but still needs consideration in persons with abrasion injuries that involve contact with soil.