This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Spores of Exserohilum rostratum, stained blue. Notice the brown pigment of the cell walls; this is melanin, the same pigment that darkens human skin. These spores can reach 125 micrometers long under the right environmental conditions. Spores of this species are highly variable. Image source and copyright: Glenn Roberts. Used with permission
Perhaps like Moselio Schaechter and me, you were surprised to hear the identity of the fungal pathogen in the New England Compounding Pharmacy fungal meningitis outbreak: Exserohilum rostratum. Unlike outbreaks caused by names we see regularly -- influenza, norovirus, E. coli, Salmonella, Listeria, etc. -- Exserohilum is not a name that is likely to have ever seen the front page of the New York Times before, much less newsprint. In spite of spending two years studying fungi, I'd never heard of it -- and few of the mycologists I asked about it knew much about it either.
Curious, I decided to track down some folks who might have an idea about what this fungus is and what it normally does in the environment. I also wanted to know if there was anything special about its biology that might have explained why it ended up in three lots of injectable steroid, whence it has sickened more than 400 and killed more than 30.
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I ended up finding the now-retired scientist who named the genus -- Kurt Leonard -- and who spent years studying its interactions with corn and other grasses back in the 1970s. I also found an on-the-brink of retirement medical mycologist at the Mayo Clinic who, in spite of 40 years of experience at the Mayo, was every bit as surprised as I was by the fungus's identity. You can read more about it in the news article I wrote for Scientific American here.