Thursday, 25 June 2009

Darwins' fungi

Darwins Fungus (Cyttaria darwinii)
Charles Darwin was born two hundred years ago this year (1809). His contributions to how we understand the natural world were many and varied, culminating in the publication of his book 'On the Origin of Species by Means of Natural Selection' published in 1859.

Darwin was an avid collector and contributed many thousands of species to the British Museum, perhaps most famously during his voyages to the Galapagos Islands. Some of these specimens show the multitude of small differences that Darwin hypothesised constituted adaptions to the local environments of particular islands within the archipelago, caused by natural selection - the driving force of evolution.

Some of the specimens Darwin collected were fungi (mainly fruiting bodies which at that time were thoughtby many to be simple plants) and these are now stored at the Royal Botanic Gardens at Kew, London, UK along with a vast collection of 1.2 million species of fungi including every species of Aspergillus.

This massively important collection, originating 20 years after Darwin published his most famous book, is one of the worlds most complete collections of fungi and forms a resource available to all scientists around the world.

Friday, 19 June 2009

Taxanomic advances lead to better diagnosis & treatment

Invasive aspergillosis is by far most commonly caused by Aspergillus fumigatus. This is an infection that is notoriously difficult to diagnose and it is important to get the diagnosis right as quickly as possible.

Modern techniques to precisely identify different species and strains have started to reveal that different isolates from what was previously thought to be a single species can actually belong to a different groups within that species definition.

What we thought was one fungal species seems to be several different 'species'. To some extent this conclusion might be academic - the differences can seem quite small. This begs the question Are these differences important?

Aspergillus fumigatus is one of the species that have been shown to actually be several slightly different 'subspecies' so it should be possible to look for clinical differences between those subspecies.

A recent paper does precisely that - it looks at a series of 36 isolates (taken from infected patients) that were formerly identified as A. fumigatus and found that they were in fact a group of fungi now named Aspergillus subsection fumigati subgenus fumigati. 4 of the isolates were identified as Neosartorya udagawae (NB Neosartorya is simply the name for the sexual state of Aspergillus).
Furthermore the research paper shows that infections by N. udagawae behaved quite differently to A. fumigatus. The infections were much longer lasting - 35 weeks compared with 5 weeks for A. fumigatus and tended to need a higher dose of antifungal medication.

We thus have an example of how having a much more refined method of identifying the infecting Aspergillus strain could help make the treatment of that infection more effective, improving medical care to the patient.

Friday, 12 June 2009

Detection of hidden moulds

Moulds are notoriously difficult to find. They love damp, dark places, shunning the cleansing effects of sunlight in particular. All they need to grow is moisture and an adequate food source, and these can be found in the most unlikely of places under flooring, in wall cavities and behind cupboards for example.

Detection of moulds when they are growing in inaccessible areas is often impossible without resorting to expensive damage to a property - if none is found then there are hefty repair bills to be paid not to mention the time it takes to carry out the work in the first place.

There has long been a need for a quick, cheap and reliable method for the detection of mould growth in buildings and the solution might have been found at last. It has long been known that moulds emit vapours as they grow, known as volatile organic compounds (VOC).
A recent paper by Moularat attempts to establish the characteristic pattern of VOC's emitted by moulds growing on building materials. They measured the VOC's being emitted by uncontaminated building materials and compared them with those emitted by materials infested with moulds.

Despite the finding that VOC's emitted by moulds accounted for only 1% of all the VOC's emitted by contaminated building materials, they were able to find a characteristic fingerprint of VOC for moulds growing in buildings and successfully validated it by provings the usefullness of their findings in 11 test buildings. All that was needed to carry out the analysis was a sample of air from within the building.

This study was restricted to the use of 3 species: Aspergillus niger, A. versicolor, Penicillium brevicompactum and relatively few building materials so needs to be expanded but clearly suggests a way forward in this most difficult area of envoronmental health.

Friday, 5 June 2009

Success in the Treatment of Fungal Infection of Transplant Patients

Patients who have received a new organ are usually partially immunocompromised in order to prevent rejection of the organ. This unfortunately leaves them vulnerable to infection with fungal infection being one of the most difficult to treat. Invasive Aspergillosis has a high mortality rate in patients like these and intensive efforts are focussed on improving this situation.

This study uses one of the newest antifungals, voriconazole, and one of the oldest in a new form, inhalable amphotericin. Both are fungicidal and attack different targets so should work together well in combination.

The drugs are used prior to the transplant to attempt to offer prophylactic protection to all patients and are then carried on throughout the transplant process. A total of 53 patients took part.
In the control group 3 patients developed invasive aspergillosis whereas in those patients that reeived voriconazole and inhaled amphotericin there were no cases at all.

There is thus a strong indication that this new combination of drugs offers better protection than the combination of older antifungals used in the control (itraconazole, fluconazole & nystatin).

We cannot say that protection against invasive aspergillosis is complete as this was not a very large trial, but this is certainly another step in learning how best to use the antifungals we have to prevent severe aspergillosis.

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