Super-Sized Spores Make Fungal Infections More Deadly Possibly Explaining Victims in Missouri (ScAm)

[eppur_se_muova]

By Katherine Harmon | Jun 17, 2011 08:45 PM

This season's tornado outbreak in the U.S. left some unusual casualties in its wake. At least three people have reportedly died from a virulent fungal infection, and several more remain infected, following the storms that struck Missouri last month.

Such severe fungal infections are rare but can be fatal if allowed to spread throughout the body—especially for people with compromised immune systems. A fungus's severity had been thought to be a factor of its type or method of spreading. But new research suggests that there is one key determinant in how deadly a fungal infection is going to be: spore size.

The pathogenic species of Mucor circinelloides can produce spores that are about 20 microns long—more than five times the size of other spores from the same species. Although smaller spores are more adept at lodging in vulnerable tissue, such as the lung, these super-sized spores are less vulnerable to attack from the body's immune systems. In particular, they seem to be too large to fall prey to macrophages, which are usually charged with consuming and killing harmful invaders. Instead, these large fungal spores overpower the macrophages and kill them, making the body more vulnerable to further infection.

To better understand why large spores are so dangerous, researchers recently engineered small spores of M. circinelloides to go into overdrive growth in the lab. The spores started behaving more like the larger breed, skipping a middle growth phase and taking off into explosive growth. The hope is that getting a handle on that accelerating process will help scientists "to find a way to arrest them in the smaller stage before they grow into more virulent, larger spores," Soo Chan Lee, of the Department of Molecular Genetics and Microbiology at Duke University Medical Center, and co-author of the new study, said in a prepared statement.

The findings, published online June 16 in PLoS Pathogens, reveal the insidious power of "cell gigantism, which lets pathogenic fungi establish infection in the hosts" before the jumbo-sized spores take over, Joseph Heitman, chair of the same department at Duke and co-author of the study, said in a prepared statement.
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more: http://www.scientificamerican.com/blog/post.cfm?id=super-sized-spores-make-fungal-infe-2011-06-17
orginal paper: http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1002086;jsessionid=794CB4E4C933A4A649A0C3DEE5021625.ambra01
PLoS is the Public Library of Science, published on-line, peer-reviewed and open-access.