Monday, 24 August 2009

Risk of Mycotoxins Associated With Hail Damaged Corn

There is very little risk of infection of most agricultural plant crops unless the crop is damaged or stressed in some way. In a way this is similar to animals and people - aspergillosis can only take hold if the person or animal is already vulnerable to infection in some way.

In crops like maize and other 'grass-like' plants the major stress can often be shortage of water while the plant is growing or too much water during harvest time (which makes the harvest damp and requires that it is dried before storage).

There are other stresses that the farmer has to contend with in order to ward off Aspergillus and other fungi and one of those is physical damage. If a leaf breaks off or is bruised the 'wound' can be vulnerable to infection, so it is easy to see that if a crop is subjected to heavy hailstorms at the wrong time during its growth cycle (e.g. as the head or fruit is becoming quite large or ripening) then hailstones, if large enough, can severely bruise the crop. Aspergillus can readily then infect the damaged parts.

This story covers that risk, and the consequential risk of mycotoxins should the crop become infected with mycotoxin-synthesising Aspergillus to a large extent.

Friday, 21 August 2009

Tobias M. Hohl honoured for work on Aspergillus fumigatus

More recognition for work carried out on Aspergillus has been announced.

Quote from the American Society for Microbiology website:

Tobias M. Hohl is honored for his research on the interaction of Aspergillus fumigatus and the pulmonary innate immune system. Hohl earned his M.D.- Ph.D. from the tri-institutional program of Weill Medical College and Graduate School of Medical Sciences of Cornell University, Memorial Sloan-Kettering Cancer Center, and Rockefeller University, New York. While a Research Fellow at Memorial Sloan-Kettering Cancer Center, Hohl studied chemokine induction and signaling pathways in macrophages exposed to A. fumigatus. He learned that Dectin-1, a receptor expressed on dendritic cells and macrophages, binds β-glucans on the surface of germinating A. fumigatus conidia. Hohl showed that β-glucans are expressed in state-specific fashion on geminating A. fumigatus, thereby, restricting the inflammatory response to germinating but not dormant fungal spores.

His work demonstrated for the first time how the mammalian immune system recognizes Aspergillus infections; it was published in PLoS Pathogen.

Friday, 14 August 2009

Experimental evidence that antibiotics can trigger allergy & asthma

Role of antibiotics and fungal microbiota in driving pulmonary allergic responses

It has been hypothesised (the "hygiene hypothesis") over the last few decades that the taking of antibiotics has a role in the increase in asthma and allergy observed over the same time. This paper describes the creation of a mouse model for antibiotic-induced disturbance of the microbial flora in the gut. Once the mice have been given antibiotics they become susceptible to an allergic airway response to stimulus by Aspergillus fumigatus spores. If the mice are not given antibiotics they do not develop the allergic response.

This is the first experimental demonstration that antibiotics and gut flora can influence allergic airway disease, and highlights the concept that events in a distant mucosal site such as the gut can play an important role in regulating immune responses in the lungs.

Friday, 7 August 2009

Mold-free tea

Tea plant
There are some specialist teas that are fermented by Aspergillus and this has apparently led to a widespread misunderstanding amongst those people who consider themselves to have problems eating food that contains some Aspergillus material or other molds. They are tending to avoid all teas as potentially containing traces of Aspergillus.

This article points out quite rightly that most tea sold in the western world is not fermented using Aspergillus but is in fact prepared using a quite different process called 'oxidation' - a mold free process where crushed leaves are left for their internal enzymes to carry out the natural oxidation process for varying amounts of time (adjusted according to the final taste required) and are then heated to stop the oxidation and dry out the leaves. The timing of the heating and drying stage is crucial to prevent mould growth.
We wrote an article on this issue some time ago and noted at that time that most tea is made by a mold-free process.

Having said that it would be very difficult to describe tea as an 'Aspergillus-free' drink as by its nature it is plant material that will be exposed to Aspergillus at various times in its life so the leaves will always be likely to hold some Aspergillus spores.
In fact the same would go for most plant foods as Aspergillus is an important component of soil and most plant material will have been in contact with soil and windblown soil. The amount of mold contaminating the plant material is probably very small and some will probably be washed off during preparation but will still not be completely free of Aspergillus material.
This is not a problem for most people and we have no reliable information telling us that anyone is badly effected by eating plant food carrying this much Aspergillus - even those who have increased allergy to this fungus.

Fermented teas are of course completely different. They have been cultured with the mould and will contain many thousands of times more Aspergillus material compared with non-fermented tea.

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