Distribution of mycotoxins in fungal structures

Abstract

Exposure to mycotoxins associated with small fungal fragments may cause adverse health effects. Current air sampling methods may not detect such fragments and may cause researchers to underestimate fungal exposures. Understanding how time and substrate affect the distribution of toxins and their release into the environment can strengthen estimates of potential risks of exposure to these toxin-carrying particles. This research investigated the influence of time and growth substrate on the amount and distribution of mycotoxins in fungal structures and particles released from the fungal colonies. A common, toxin-producing, indoor mold, Aspergillus versicolor, was inoculated on two different agars: Malt Extract (MEA) and Wallpaper Paste (WPA). Fungal material was collected both by coring the plates, and by washing the plates with sterile water and glass beads at weekly intervals from one to six weeks. The wash water suspensions were filtered through 20- and 1-micron filters and lyophilized. The filters and the lyophilized wash water samples were extracted with methanol and analyzed for both sterigmatocystin and ergosterol (a marker of fungal growth). Results indicate that overall growth and toxin levels are higher on MEA than on WPA, but when standardized against ergosterol, sterigmatocystin levels on WPA are higher. Measurable amounts of ergosterol and sterigmatocystin are detectable in the lyophilized wash water. Ergosterol and sterigmatocystin increase steadily over six weeks on WPA, but peak around 3-4 weeks on MEA. Our conclusions are that small fungal fragments can carry toxins at levels that could deliver biologically significant doses if the fragments were inhaled into the deep lung.