Environmental Attributes Influencing the Distribution of Burkholderia pseudomallei in Northern Australia.

Factors responsible for the spatial and temporal clustering of Burkholderia pseudomallei in the environment remain to be elucidated. Whilst laboratory based experiments have been performed to analyse survival of the organism in various soil types, such approaches are strongly influenced by alterations to the soil micro ecology during soil sanitisation and translocation. During the monsoonal season in Townsville, Australia, B. pseudomallei is discharged from Castle Hill (an area with a very high soil prevalence of the organism) by groundwater seeps and is washed through a nearby area where intensive sampling in the dry season has been unable to detect the organism. We undertook environmental sampling and soil and plant characterisation in both areas to ascertain physiochemical and macro-floral differences between the two sites that may affect the prevalence of B. pseudomallei. In contrast to previous studies, the presence of B. pseudomallei was correlated with a low gravimetric water content and low nutrient availability (nitrogen and sulphur) and higher exchangeable potassium in soils favouring recovery. Relatively low levels of copper, iron and zinc favoured survival. The prevalence of the organism was found to be highest under the grasses Aristida sp. and Heteropogon contortus and to a lesser extent under Melinis repens. The findings of this study indicate that a greater variety of factors influence the endemicity of melioidosis than has previously been reported, and suggest that biogeographical boundaries to the organisms' distribution involve complex interactions.

Sago haemolytic disease: towards understanding a novel food-borne toxicosis.

Sago haemolytic disease is a rare but sometimes fatal disease found primarily in the coastal regions of Papua New Guinea and among groups in which sago is a primary source of carbohydrate. It has been known since 1961 and fungi consistently have been suspected of being involved. Investigations carried out on stored sago and samples recovered from poisoning episodes have failed to indicate the consistent presence of mycotoxins. However, fungi (especially Aspergillus, Fusarium, Penicillium, Trichoderma) with strong haemolytic activity have been associated with sago, particularly when stored in open-weave baskets and sago-leaf-wrapped bundles. The haemolytic activity has been attributed to fatty acids (principally oleic, palmitic, linoleic) contained primarily in the fungal hyphae. It is hypothesized that when these acids are released through hyphal breakdown during digestion and are present in individuals with a low serum albumin level, free fatty acid excess occurs resulting in red cell membrane destruction and intravascular haemolysis. In extreme cases, blood transfusion is required. Methods of storage providing high levels of access to oxygen favour the development of fungi: eg, leaf-encased bundles and open-weave storage favour growth over that seen in starch stored under water, such as in earthen vessels. Ensuring storage does not exceed 3-4 weeks, encouraging anaerobic conditions of the starch and maintaining protein nutrition in communities where sago is relied upon should alleviate outbreak episodes.

Haemolytic fungi isolated from sago starch in Papua New Guinea.

Sago haemolytic disease (SHD) is a rare but often fatal illness linked to consumption of stale sago starch in Papua New Guinea. Although the aetiology of SHD remains unknown, mycotoxins are suspected. This study investigated whether fungi isolated from Papua New Guinean sago starch were haemolytic. Filamentous fungi and yeasts from sago starch were grown on sheep blood agar and some on human blood agar. Clear haemolytic activity was demonstrated by 55% of filamentous fungal isolates, but not by yeasts. A semi-quantitative bioassay was developed involving incubation of human erythrocytes with fungal extracts. Extracts of cultures of Penicillium, Aspergillus and Fusarium all caused rapid haemolysis in the bioassay. Partial fractionation of extracts suggested that both polar and non-polar haemolytic components had haemolytic activity in vitro. Further work is warranted to identify these metabolites and determine if they play a role in SHD.