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)
Next WMC: 5-10th August, 2016, Hawaii
Picture courtesy Melioidosis.Info
Lovers of opera may remember notes that appeared on this blog previously. We got about as far as it being all over when a gravitationally advantaged lady sang. But we didn’t get in a mention of the ring cycle: that major work of Wagnerian genius. This time around, we’re taking a look at another kind of valkyrie. We’re back to our tiny airborne nemesis; the malaria parasite Plasmodium.
Malaria info source
In ‘All your malarias‘ we brought together a body of teaching materials on malaria. In our parasitology section you could find a number of ring forms, and the Plasmodium life cycle. But we left out the new star of the ring; Plasmodium knowlesi. The initial work was done by a group at UNIMAS in Kuching, Sarawak. Subsequent reports map out a patchy distribution through Southeast Asia that overlaps areas where you can find macaques and the mosquito Anopheles leukophyrus.
Four Pl. knowlesi trophozoites and a schizont (R). The trophozoites show features that can be found in Pl. falciparum and Pl. malaria.
Pl. knowlesi can cause serious human infection, particularly in people travelling to remote parts of Southeast Asia for work or pleasure.
Laboratory confirmation is a bit more complicated than for the other four Plasmodium species because young trophozoites appears as ring forms, similar to the ring forms of Pl. falciparum, and older trophozoites can appear in band forms like Pl. malaria. An additional problem is that rapid diagnostic tests are not yet geared up to detect Pl. knowlesi. This makes molecular methods like PCR assays more attractive for clinical labs with only sporadic demand for malaria microscopy.
Several useful features have been described. Taken together, this presents s different picture from Pl. falciparum and Pl. malariae but individual cases can present the microscopist with a significant challenge. You can obtain a useful chart and more detailed information on the CDC Clinical Parasitology site.
- varied types of trophozoite at early and mature stages including ring forms, multiple rings per erythrocyte, multiple chromatin dots per ring, signet ring appearance and appliqué forms at the red cell periphery, band forms and more amoeboid distribution within the red cell
- malaria pigment may be present in the erythrocyte
- schizonts have up to 16 merozoites inside, and a prominent nucleus
- macrogametocytes of both genders are round
On the Asian bread trail
The crazy bug hunters have been at it again. This time they took to the air courtesy a mixed bag of budget Asian airlines. They converged on the northern Malaysian city of Ipoh for a field applications worship. There we were welcomed by the staff of University of KL’s Royal College of Medicine Perak. In Ipoh they take their hospitality very seriously. We were sampling fresh local bread less than 24 hours after arriving. Here is a view from the top floor of their rather smart building, looking over a nearby mosque.
And this is the first of our encounters with freshly made bread. It was served as an accompaniment to Moroccan lamb, tabouleh and other Arabic delicacies. By the time we’d made it back home, the team had sampled naan, dosai, pakoras and the wonderfully calorific murtabak. Plain white bread is, well, just plain by comparison.
Another bread for the team
The bug hunters did get down to some serious field work before knuckling under with their set of automatic pipettes. Here they are among the tea bushes in the Cameron Highlands (home of the giant strawberry, for Australian collectors of bizarre giant replicas). The last time we were in tea growing country was June this year when we deployed our field lab to Central Province, Sri Lanka. Our photographer captured the moment the yellow tops came into evidence among the bushes.
Once in the lab it was time to sweat the small stuff. That’s how we earn our crust, working systematically through a series of samples with our Lab Without Walls field portable equipment set. Here you can see a Micrognome demonstrating the use of a Mk I head as a substitute for an anglepoise lamp, while one of the workshop participants dispenses PCR reagents.
two legged lamp stand
And the results of our bread run?
- blood culture confirmatory PCR panel run on positive cultures same day
- 5 of 6 suspected Burkholderia isolates confirmed as B. pseudomallei AND shown to be SE Asian clade by PCR assay
- 3 of 5 hospital admissions shown to have dengue virus genotypes 1 or 2 on same day
- hands on familiarisation with field applications of molecular microbiology in national workshop
- lectures on severe sepsis, melioidosis and other activities of the Lab Without Walls
out of the box and into action
Ipoh has a great reputation for Asian food and is now a direct budget flight from Singapore.
The mosquito midgut is hostile to Plasmodium parasites and acts as a bottleneck to their development within the Anopheles gambiae mosquito. A recent investigation of gene regulation and protein in mosquitoes identifies previously unrecognised mosquito factors. The full version of the paper is in production, but the announcement will interest biologists who want to learn how to exploit nature in the fight against malaria.
Here’s a whistle-stop summary for those who don’t have to time to click their way to five minutes of well-researched entomology:
- mosquito. 1575-85; Spanish equivalent to mosca, fly, from Latin, musca, fly, meaning little fly
- Anopheles. 1895-1900; Greek anopheles, useless, hurtful, harmful, from an(without)+ opheles(profit): the genus responsible for transmission of malaria
- Culex. from Latin, gnat or midge: a large genus of mosquito whose adult feeds with her body parallel to the surface on which she stands
If you need to explain away how quickly time disappears, try clicking on malaria matters.
There is a logic to mosquito names.
No, the Micrognome hasn’t disappeared in a circular argument; a confusion of etymology with entomology. Far from it. Back from his recent travels in the Kimberley and following his nose, or maybe even his proboscis, he discovered a treasure trove of biological naming words today.
For those with the time to look, layer upon layer of knowledge has been wrapped up in the names given to all those thousands of mosquito species (how the mosquito got is name). There is a truly wonderful catalogue of Anopheles mosquito nomenclature in which both entomologists and etymologists can lose themselves for many hours on a slow Sunday afternoon.
Now here’s a thought to reward the careful reader who takes the trouble to get to the bottom of the page; if we were true to the Spanish origin, the plural of mosquito would be ‘mosquitos’, and not the Anglicised mosquitoes we normally use.