Conference report: 7th World Melioidosis Congress
Bangkok, Thailand, 18-20th September, 2013
The results of the last three years of intensive research were reviewed this week in Bangkok in a programme packed with basic and applied biomedical science. The triennial melioidosis congress has gone far since first described as a world meeting in Perth 12 years ago. Numbers attending the congress have expanded over the last decade from just over 100 to more than 300 delegates. Publications on melioidosis and its bacterial cause continue to expand knowledge without any signs of abating.
Some of the achievements of the last three decades were covered in a comprehensive review of melioidosis in Thailand by Wipida Chaowagul and Nick White. The earliest history of melioidosis was dealt with by David Dance in his tribute to Alfred Whitmore, who discovered the infection a century ago. Here are some of the other highlights:
- Epidemiology. Cases of melioidosis continue to trickle in from south and central America including Brazil and Puerto Rico, the gaps in the melioidosis map of Africa are beginning to fill, and other countries now searching for the infection systematically include Laos and Bangladesh. A world map project now shows the current state of worldwide melioidosis distribution. More than 20 new cases are now reported in India where a melioidosis collaborative network has formed. In Thailand, melioidosis is now the third commonest fatal infection.
- Clinical presentation. Systematic review of culture-confirmed cases underlines the wide range of clinical presentations from rapidly progressing septicaemic infection, to the more chronic skin and soft tissue infections. One study emphasised the importance of considering melioidosis in patients with pneumonia that test negative for tuberculosis. Serology is no longer considered a suitable method for clinical diagnosis, though it evidently still has epidemiological value.
- Treatment. A helpful review from the Northern Territory prospective case study suggested that a longer period of initial intravenous therapy might reduce the relapse rate, particularly in patient groups that were difficult to sustain on prolonged eradication therapy.
- Pathogenesis and immunology. The ability of Burkholderia pseudomallei to penetrate mammalian cells, avoid intracellular destruction and then fuse adjacent host cells are important features of this facultative intracellular bacterium. Key components of this cellular pathogenesis pathway are a collection of three type three secretion systems and a more recently discovered type six secretion system. The balance between pro- and anti-inflammatory innate immune responses and downstream pathways was reviewed, amidst a flurry of acronyms of increasing length (e.g. TLRs, PAMPs, DAMPs, TREM-1, IRAK-1 and NETS). Antioxidant defences and the importance of glutathione to defence against intracellular bacteria including B. pseudomallei are attracting more attention for basic research. Much detail has been added on pathways and regulation, but significant obstacles remain in the search for a unifying mechanistic understanding of cellular pathogenesis.
- Vaccine development. Advances in basic sciences are usually judged by their practical consequences. It was therefore pleasing to see so much work on vaccine development including improved improved delivery via gold nanoparticles and promising preliminary results in model systems with killed non-pathogenic near-neighbour Burkholderia thailandensis. But a word of caution was noted by one of the keynote speakers – even the most promising vaccine candidates are likely to take many years before they are ready for general use.
- Environmental microbiology. Melioidosis is an infection of environmental encounter, so this part of the World Melioidosis Congress has special interest throughout the wider melioidosis research community. Careful mapping in the Northern Territory combined with field studies has identified a role for grasses in sustaining B. pseudomallei in the rhizosphere. Studies of clinical and environmental B. pseudomallei isolates highlighted the role of unchlorinated domestic water supplies as a potential source of infection. Careful studies of dry soils from northern Queensland showed that B. pseudomallei could survive in dry soils longer than previously known, and then increase in numbers after wetting. Attempts at biocontrol of environmental B. pseudomallei by use of B. thailandensis have been disappointing so far.
Western Australian institutions represented
- University of Western Australia, School of Pathology and Laboratory Medicine (3)
- PathWest Laboratory Medicine, Department of Microbiology, Nedlands (2)
- Curtin University, School of Biomedical Sciences (1)
- Telethon Institute of Child Research (1)
- What is melioidosis?
- Facebook page
- Occupational risk
- The aftermath of the WA outbreak
- World melioidosis map
Next WMC: 5-10th August, 2016, Hawaii